Carper was born in Beckley, West Virginia, the son of Mary Jean (née Patton) and Wallace Richard Carper. He grew up in Danville, Virginia, and graduated from Whetstone High School in Columbus, Ohio. He then graduated from the Ohio State University in 1968, where he was a midshipman in the Naval ROTC and earned a degree in economics. At Ohio State, Carper became a member of the Beta Phi Chapter of the Delta Tau Delta fraternity.

Serving as a Naval Flight Officer in the U.S. Navy from 1968 until 1973, he served three tours of duty in Southeast Asia during the Vietnam War. He remained in the U.S. Naval Reserve as a P-3 aircraft mission commander for another 18 years and retired with the rank of Captain (O-6). Meanwhile, he moved to Delaware and earned a MBA from the University of Delaware in 1975, after which time he went to work for the economic development office for the State of Delaware.

After receiving his MBA degree in 1975, Carper went to work for the State of Delaware’s economic development office. In 1976, after developing good relationships with members of the state party leadership, he took out a $5,000 personal loan to fund his campaign for the Treasurer of Delaware. After convincing the party leaders, and later the voters, that he was the right person to be Delaware State Treasurer, he defeated the favored Republican Party candidate, Theodore Jones. He served three terms, from January 18, 1977 through January 3, 1983, during which time he oversaw the development of Delaware’s first cash management system.

Carper has been married twice, first in 1978, to Diane Beverly Isaacs, a former Miss Delaware, who had two children by a previous marriage. They divorced in 1983. In a 1998 interview, Carper admitted, “I slapped my then-wife, Diane, during a heated argument,” describing it as a mistake. A New York Post article in 1982 stated that Carper hit Isaacs “so hard he gave her a black eye” and that his wife’s two children from a previous relationship “were slapped around and bruised by Carper for doing such things as leaving the family dog on the bed.” Carper denied these claims.

It took a considerable amount of persuasion on the part of U.S. Senator Joe Biden and others to convince Carper to leave his obscure, but safe, position as Treasurer and compete for Delaware’s only seat in the U.S. House of Representatives in 1982. Thomas B. Evans, Jr., the incumbent Republican, was running again, and although he had been caught in a compromising “association” on a golfing trip with the young lobbyist Paula Parkinson, he was still a formidable and well-connected politician.

Carper went on to serve five terms in the U.S. House of Representatives. He won his second term in 1984, by defeating Elise R.W. du Pont, the wife of retiring Governor Pierre S. du Pont, IV. He then enjoyed easy victories over Republicans Thomas S. Neuberger in 1986, James P. Krapf in 1988 and Ralph O. Williams in 1990. A U.S. Representative, he was a member of the U.S. House Committee on Banking, Finance and Urban Affairs and the U.S House Committee on Merchant Marine and Fisheries. He chaired the House Subcommittee on Economic Stabilization. In these positions he worked to allow banks into the securities business and to discourage the dumping of sludge into the ocean.

Carper married Martha Ann Stacy in 1985, and with her he had two children, Christopher and Benjamin. The family are members of Westminster Presbyterian Church in Wilmington, Delaware.

During his years in the U.S. House of Representatives Carper sought to gain better control of the Democratic Party organization in Delaware in hopes of someday becoming governor. Heavily Democratic and with over half of the population of the state, New Castle County was the key. Its Democratic organization was controlled by Eugene T. Reed, a former ironworker, and an old-time political party boss who was then among several politicians in both parties implicated in illegal money raising practices. To address this corruption and rescue the reputation of the Democratic Party, Carper recruited Joseph E. Reardon, a DuPont Company chemist, as a candidate for New Castle County Democratic Party chairman. By early 1989, he had succeeded in getting Reardon elected, and Reardon replaced Reed at the head of a newly reformed party organization. In 1990 Carper faced a primary challenge from a Reed ally, Daniel D. Rappa, after winning, he went on to win election to his fifth term as U.S. Representative.

In the small and intimate political community of Delaware, important decisions are often made by a consensus of leaders from both parties. So it was in 1992, when popular incumbent (Republican) Governor Michael Castle was forced to retire owing to term limits. The result was what became known as “the Swap.” Castle ran for Carper’s seat in the U.S. House of Representatives and Carper ran for Governor. Neither faced any significant opposition and Delaware retained the services of two very popular office holders representing both major parties.

Thus, in 1992, Carper was elected Governor of Delaware, defeating the Republican candidate, B. Gary Scott. He ended up serving two terms. As a moderate, business-oriented Democrat who followed two very competent and popular Republican administrations, those of Pierre S. du Pont, IV and Castle, Carper chose to govern in much the same way they had over their combined 16 years in office, adding to the mix his special interest in and talent for economic development and business recruitment. Two particular successes were his prevention of the closure of the General Motors automobile operation near Newport, Delaware and the state’s victory in the competition with Pennsylvania for the location of the headquarters of the pharmaceutical giant, AstraZeneca.

Carper’s independent, New Democrat approach made him popular among voters, but caused grumbling among old line Democrats, particularly union leaders, who complained that not enough of them were being awarded patronage jobs after the many years of Republican control. In an era of increasingly bitter, partisan politics, Carper’s actions and policies placed him at the political center, in keeping with Delaware’s consensus style of governing. One atypical example of Carper’s bipartisan cooperation occurred in 1995, when Carper’s former House colleague Bob Dornan was running as a candidate in the 1996 Republican primary for the Presidential nomination. At a stop in Wilmington, Delaware for a train on which Dornan was traveling, Carper was waiting on the platform, dressed as a pregnant woman, carrying a sign that said “Dornan Is the One”. Dornan recognized Carper, and went along with the joke, which Carper had coordinated with the Republican State Committee of Delaware.

The elections of 2000 promised to bring a change in Delaware’s political lineup. For 16 years, the same four people had held the four major statewide positions — Governor Carper and fellow Democratic Senator Joe Biden, and Republicans U.S. Representative Michael Castle and Senator William V. Roth, Jr. Because of gubernatorial term limits, Carper had to retire from the post. He wanted to run for the Senate against the incumbent Roth. Roth would not retire voluntarily and fellow Republican Castle would not force him into a primary. Carper declared his candidacy in September 1999. In a contest between two popular and respected politicians, the issue seemed to be Roth’s age: Roth was 79, versus Carper’s relative youth. Although Roth started the campaign with a 2-to-1 spending advantage, Carper went into the final month with more than $1 million on hand. Carper defeated Roth by twelve points, 56% to 44%. Roth received more votes than Republican Presidential candidate George W. Bush, suggesting that the strength of the Democratic turnout for the presidential election was a key factor in Carper’s victory. Some commentators attributed Roth’s defeat to his age and health, as he collapsed twice during the campaign, once in the middle of a television interview and once during a campaign event.

Carper has a mixed record on abortion issues. In 2003, Carper was one of 17 Democrats who broke with the majority in their party by voting to ban partial-birth abortion. He also voted against banning abortion after 20 weeks of pregnancy, but he voted to ban the use of federal funds for abortion. In 2018, he opposed President Trump’s proposal to defund Planned Parenthood. Carper was given a 50% rating by NARAL Pro-Choice America indicating a mixed record on abortion, according to their scoring, and a 25% rating from the pro-life National Right to Life Committee.

He served with the Democratic minority in the 108th and 109th Congresses, and was part of the Democratic majority in the 110th Congress. At the beginning of the 107th Congress, the Democratic Party was in the minority, but later held the majority. Carper is a member of the moderate Democratic Leadership Council (DLC), of which he currently serves as Vice-Chairman. In December 2004, Carper became a part of the Senate Democratic Leadership. As a member of a four-person “Executive Committee”, he is one of four deputy whips. David Broder of the Washington Post has called Carper “a notably effective and non-partisan leader, admired and trusted on both sides of the aisle.”

Carper sought re-election to a second term in 2006. He was unopposed in the Democratic primary and faced off against Republican candidate Jan C. Ting. Ting was a professor of law who had narrowly beaten airline pilot Michael D. Protack in the Republican primary. Carper was easily re-elected in a landslide win, beating Ting 67% to 27%.

Carper signed a law as Governor defining “marriage as between a man and a woman,” but he also voted as a Senator against the Federal Marriage Amendment, a proposed constitutional amendment to ban gay marriage. He also voted against banning gay marriage again in 2006. In 2013, Carper announced that he now supports same-sex marriage.

Carper proposed the creation of a National Park in Delaware, the Coastal Heritage Park, in four locations along the Delaware River and Delaware Bay. In January 2009 Carper briefly chaired a Senate Committee on Environment and Public Works hearing on the Tennessee Valley Authority’s coal ash spill in Kingston, Tennessee. However, he did vote for Keystone XL Pipeline, but has since expressed disappointment in that vote.

Carper and George Voinovich of Ohio proposed a 25-cent raise in the federal gasoline tax; 10 cents would go to pay down the debt and the rest toward improving the nation’s infrastructure. The measure was proposed in November 2010. The measure did not pass.

Carper co-wrote the “Protecting Cyberspace as a National Asset Act of 2010” introduced on June 19, 2010, by Senator Joe Lieberman (Senator Susan Collins is the third co-author of this bill). If signed into law, this controversial bill, which the American media dubbed the “Kill switch bill”, would grant the President emergency powers over the Internet. All three co-authors of the bill, however, issued a statement claiming that instead, the bill “[narrowed] existing broad Presidential authority to take over telecommunications networks”. Carper was quoted as saying that the bill “would create a National Center for Cybersecurity and Communications in the Department of Homeland Security, with a Senate-confirmed director to oversee security of the federal government’s computer networks. The center would also identify vulnerabilities and help secure key private networks – like utilities and communications systems – that, if attacked or commandeered by a foreign power or cyberterrorists, could result in the crippling of our economy.”

In May 2010, Carper introduced an amendment to limit state regulators from enforcing consumer regulations on national banks and their subsidiaries. It would also remove a Senate legislative measure requiring the Office of the Comptroller of the Currency to find a “substantive standard” on regulation, before the office could move to preempt. The White House opposed Carper’s amendment. The amendment passed by a vote of 80–18.

On May 14, 2011, the Wall Street Journal criticized a postal-bailout bill co-sponsored by Carper and Susan Collins (R-Maine). The bill would give $50–$75 billion to USPS, and would underwrite pension obligations for retired postal workers. The bailout would cost three times the savings of the 2011 federal budget.

On September 21, 2011, The Wall Street Journal noted that President Obama’s job-creation plans were drawing resistance from Senate Democrats. The article quoted Carper as saying, “I think the best jobs bill that can be passed is a comprehensive long-term deficit-reduction plan. That’s better than everything else the president is talking about combined.”

As the 2012 election cycle began, a Super PAC was created to oppose Carper’s re-election campaign. The Hill quoted Patrick Davis, the custodian of records and agent for Renew Delaware as saying: “Tom Carper has served in the United States Senate for a long time and has been part of the downturn in our economy.” Delaware Politics noted that the election would be costly for the Republican candidate and that the popular Carper was heavily favored to win a third term in office. A Carper spokesperson, Emily Spain, was quoted in The Hill saying that Carper was successful in his previous campaigns “because he works hard, takes nothing for granted, and puts the needs and interests of Delaware first.” Carper won the Democratic primary with 88% of the vote and faced off against the only Republican candidate who filed for the race, businessman Kevin Wade. Carper was re-elected in another landslide, beating Wade 66% to 29%.

He joined in the unsuccessful attempt to tie the Bush administration tax cuts to deficit reduction and has supported additional funding for school choice programs and charter schools. He has also sought additional funding for railroad projects and for rail security. He strongly supported legislation to limit class action lawsuits and to restrict personal bankruptcy. In addition, he is a strong proponent of free trade. In 2012, Carper sponsored a bill, eventually passed and signed into law, that required government agencies to identify $125 billion in expected waste and fraud.

Carper joined 23 other Senate Democrats in signing a letter supporting Obama taking executive action to reduce gun violence. In 2013, he voted to ban high-capacity magazines of over 10 bullets. In 2016, Carper participated in the Chris Murphy gun control filibuster. In response to the 2017 Las Vegas shooting, Carper called for common sense gun laws, specifically background checks and mental health screenings.

In April 2014, the United States Senate debated the Minimum Wage Fairness Act (S. 1737; 113th Congress). The bill would amend the Fair Labor Standards Act of 1938 (FLSA) to increase the federal minimum wage for employees to $10.10 per hour over the course of a two-year period. The bill was strongly supported by President Barack Obama and many of the Democratic Senators, but strongly opposed by Republicans in the Senate and House. Carper said that he preferred legislation that would have a greater chance of becoming law, such as an increase to only $9 an hour.

Unlike most senators, who maintain residences in both Washington, D.C., and in their home state, Carper commutes more than 100 miles by Amtrak train from his home in Wilmington to the United States Capitol. Carper says this arrangement has helped his family live a normal life despite his demanding, high-profile job. On May 12, 2015, he narrowly escaped injury when the train he took home derailed and crashed in Philadelphia shortly after he deboarded.

In August 2018, Carper was seeking his fourth six-year term in the United States Senate. Tom Carper’s campaign contributors as of 2018 included DuPont, with DuPont being his third largest contributor since 2013. Between 2013 and 2018, he received $2.1 million from political action committees. Carper was challenged from the left by Kerri Evelyn Harris, a US Air Force Veteran. She contrasts with Carper in that she advocates a single payer healthcare system, and Carper wants to keep working on the Affordable Health Care Act. Carper defeated Harris in the primary election with roughly 65% of the vote. It was Carper’s most competitive primary in his recent political history. In the general election, Carper defeated Republican opponent Rob Arlett by a landslide margin of 22.2 points, 60.0% to 37.8%.

In April 2019, Carper was one of thirty-four senators to sign a letter to President Trump encouraging him “to listen to members of your own Administration and reverse a decision that will damage our national security and aggravate conditions inside Central America”, asserting that Trump had “consistently expressed a flawed understanding of U.S. foreign assistance” since becoming president and that he was “personally undermining efforts to promote U.S. national security and economic prosperity” through preventing the use of Fiscal Year 2018 national security funding. The senators argued that foreign assistance to Central American countries created less migration to the U.S., citing the funding’s helping to improve conditions in those countries.

In January 2019, Carper was one of forty senators to introduce the Background Check Expansion Act, a bill that would require background checks for either the sale or transfer of all firearms including all unlicensed sellers. Exceptions to the bill’s background check requirement included transfers between members of law enforcement, loaning firearms for either hunting or sporting events on a temporary basis, providing firearms as gifts to members of one’s immediate family, firearms being transferred as part of an inheritance, or giving a firearm to another person temporarily for immediate self-defense.

On August 1, 2019, the Senate passed a bipartisan budget deal that raised spending over current levels by 320 billon and lifted the debt ceiling for the following two years in addition to forming a course for funding the government without the perceived fiscal brinkmanship of recent years. Carper joined Joe Manchin and Republicans Mitt Romney and Rick Scott in issuing a statement asserting that “as former Governors, we were responsible for setting a budget each year that was fiscally responsible to fund our priorities. That’s why today, we, as U.S. Senators, cannot bring ourselves to vote for this budget deal that does not put our country on a fiscally sustainable path.”

In April 2019, Carper was one of forty-one senators to sign a bipartisan letter to the housing subcommittee praising the United States Department of Housing and Urban Development’s Section 4 Capacity Building program as authorizing “HUD to partner with national nonprofit community development organizations to provide education, training, and financial support to local community development corporations (CDCs) across the country” and expressing disappointment that President Trump’s budget “has slated this program for elimination after decades of successful economic and community development.” The senators wrote of their hope that the subcommittee would support continued funding for Section 4 in Fiscal Year 2020.