From Southern California, Carter was born in Culver City in 1954 to Jim Carter, an aircraft worker, and his wife, Inge. Athletic at a young age, Carter – along with four other boys – won the 7-year-old category of the first national Punt, Pass, and Kick skills competition in 1961. A month after he turned twelve in 1966, his 37-year-old mother died of leukemia. Carter attended Sunny Hills High School in Fullerton, where he played football as a quarterback, baseball as an infielder, and graduated in 1972. He also played American Legion Baseball, and was named the 1981 American Legion Graduate of the Year.

Carter was drafted by the Montreal Expos as a shortstop in the third round of the 1972 Major League Baseball draft. Carter got his nickname “The Kid” during his first spring training camp with the Expos in 1974.

The Expos converted Carter to a catcher in the minor leagues. In 1974, he hit 23 home runs and drove in 83 runs for the Expos’ Triple-A affiliate, the Memphis Blues. Following a September call-up, Carter made his major league debut in Jarry Park in Montreal in the second game of a doubleheader against the New York Mets on Monday, September 16. Despite going 0–4 in that game, he finished the season batting .407 (11–27). His first major league hits came in both games of another doubleheader with the Mets on September 18, as a pinch hitter in the seventh inning of the opener and as the catcher in the nightcap, and the Expos swept. His initial MLB home run came on September 28 against Steve Carlton in a 3–1 victory over the visiting Philadelphia Phillies.

He and his wife, Sandy, were married in 1975. They had three children.

Carter again split time in the outfield and behind the plate in 1976 while a broken finger limited him to 91 games. He batted .219 with six home runs and 38 RBIs. In 1977, young stars Warren Cromartie, Ellis Valentine, and Andre Dawson became full-time outfielders. In mid-June, former starting catcher Barry Foote was traded to the Phillies, opening up even more starts for Carter behind the plate, with little time at other positions. He responded with 31 home runs and 84 RBIs. In 1980, Carter clubbed 29 home runs, drove in 101 runs, and earned the first of his three consecutive Gold Glove Awards. He finished second to third baseman Mike Schmidt in NL MVP balloting, whose Phillies took the National League East by one game over the Expos.

That same year, he was voted the Expos Player of the Year for the first of four times (also winning in 1977, 1980, and 1984).

Carter caught Charlie Lea’s no-hitter on May 10, 1981, the nightcap of a doubleheader split, during the first half of the strike shortened season. The season resumed on Sunday, August 9, with the All-Star Game. Carter was elected to start his first All Star Game, and responded with two home runs and being named the game’s MVP. Carter was the fifth and most recent player to hit two home runs in an All-Star Game.

Carter hit a home run in the 1984 All-Star Game to give the NL a 2–1 lead that they would not relinquish, earning him his second All-Star game MVP award. Carter’s league leading 106 RBIs, 159 games played, .294 batting average, 175 hits and 290 total bases were personal highs.

The 1984 Expos finished fifth in the NL East. At the end of the season, the rebuilding Expos chafed at Carter’s salary demands and traded him in December to the Mets for Hubie Brooks, Mike Fitzgerald, Herm Winningham, and Floyd Youmans.

In his first game as a Met on April 9, 1985, he hit a tenth-inning home run off Neil Allen to give the Mets a 6–5 Opening Day victory over the St. Louis Cardinals. The Mets and Cardinals rivaled for the National League East championship, with Carter and first baseman Keith Hernandez leading the Mets. The season came down to the wire as the Mets won 98 games that season; however, they lost the division to the Cardinals, three games ahead with 101 wins. Carter hit a career high 32 home runs and drove in 100 runs his first season in New York. The Mets had three players finish in the top ten in NL MVP balloting that season (Dwight Gooden 4th, Carter 6th, and Hernandez 8th).

In 1986, the Mets won 108 games and took the National League East by 21½ games over the Phillies. Carter suffered a postseason slump in the NLCS, batting .148. However, he hit a walk-off RBI single to win Game 5. Carter also had two hits in Game 6 which the Mets won in 16 innings.

The Mets won the World Series in seven games over the Boston Red Sox. Carter batted .276 with nine RBIs in his first World Series, and hit two home runs over Fenway Park’s Green Monster in Game Four. He is the only player to hit two home runs in both an All-Star Game (1981) and a World Series game. Carter started a two-out rally in the tenth inning of Game 6, scoring the first of three Mets runs that inning on a single by Ray Knight. He also hit an eighth-inning sacrifice fly that tied the game. Carter finished third on the NL MVP ballot in 1986.

Carter batted .235 in 1987, and ended the season with 291 career home runs. He had 299 home runs by May 16, 1988 after a fast start, then slumped until August 11 against the Chicago Cubs at Wrigley Field when he hit his 300th. During his home run drought, Carter was named co-captain of the team with Hernandez, who had been named captain the previous season.

Carter ended 1988 with 11 home runs and 46 RBIs—his lowest totals since 1976. He ended the season with 10,360 career putouts as a catcher, breaking the career mark of Detroit Tigers catcher Bill Freehan (9,941).

The Mets won 100 games that season, taking the NL East by 15 games. Heavily favored, the Mets were upset by the Los Angeles Dodgers in the NLCS. Carter batted .183 in 50 games for the Mets in 1989. In November, the Mets released Carter after five seasons, hitting 89 home runs and driving in 349 runs.

Released by the Mets after the 1989 season, Carter subsequently joined the San Francisco Giants. At age 36, he platooned with catcher Terry Kennedy in 1990, batting .254 with nine home runs. He found himself again in a pennant race in 1991 with the Los Angeles Dodgers, who finished one game behind the Atlanta Braves in the National League West.

At the end of the season, Carter returned to Montreal for his final season, obtained off waivers from the Dodgers. Carter was still nicknamed “The Kid” by teammates despite his age. In his last at-bat (in the seventh inning) on September 27, 1992, he hit a double over the head of Chicago Cubs right-fielder and former Expos teammate Andre Dawson. This hit drove in Larry Walker and proved to be the winning hit. After the hit, he was given a standing ovation. The Expos went 87-75 and finished second behind the Pittsburgh Pirates in the National League East.

After his retirement as a player, Carter served as an analyst for Florida Marlins television broadcasts from 1993 to 1996. He also appeared in the movie The Last Home Run (1998) which was filmed in 1996.

Carter was inducted into the New York Mets Hall of Fame in 2001. While the Mets have not retired number eight, it has remained unused since Carter’s election to the Hall of Fame in 2003. In 2001, Carter was elected into the Canadian Baseball Hall of Fame along with Dave McKay, and his number eight was retired by the Expos. After the Expos moved to Washington, D.C. to become the Washington Nationals following the 2004 season, a banner displaying Carter’s number along with those of other Expos stars Andre Dawson, Tim Raines and Rusty Staub was hung from the rafters at the Bell Centre, home of the NHL’s Montreal Canadiens. In Washington, D.C., Carter is recognized in the Ring of Honor at Nationals Park.

In his sixth attempt on the Baseball Hall of Fame ballot, Gary Carter was elected to the Baseball Hall of Fame along with Eddie Murray on January 7, 2003. Carter became the first Hall of Famer whose plaque depicts a player with the Montreal Expos logo. Carter had originally expressed a preference during his final playing season to be inducted wearing an Expos cap on his plaque. Given the uncertainty of the Expo franchise, Carter’s employment by the Mets organization since retiring as a player, his World Series title with the Mets, and his media celebrity during his stint in New York, Carter shifted his preference to be enshrined with a Mets cap after his election to the Hall. The New York City media strongly supported Carter’s preference to go into the Hall as a Met. Carter joked that “he wanted his Cooperstown cap to be a half-and-halfer, split between the Expos and Mets”. The final decision rested with the Hall of Fame, and Hall president Dale Petroskey declared that Carter’s achievements with the Expos over twelve season had earned his induction, whereas his five seasons with the Mets by itself would not have, saying “we want to have represented on the plaque the team that best represents where a player made the biggest impact in his career. When you look at it, it’s very clear. Gary Carter is an important part of the history of the Expos.” Carter accepted the Hall’s decision with grace, stating: “The fact I played 11 years in Montreal and the fact that the majority of my statistics and accomplishments were achieved there, it would be wrong, probably, to do it any other way.” At the induction ceremony, Carter spoke some words in French, thanking fans in Montreal for the great honor and pleasure of playing in that city, while also taking great care to note the Mets’ 1986 championship as the highlight of his career.

Carter was named Gulf Coast League Manager of the Year his first season managing the Gulf Coast Mets in 2005. A year later, he was promoted to the A-level St. Lucie Mets, and guided his team to the 2006 Florida State League championship, again earning Manager of the Year honors. In more recent years, Carter was criticized, most notably by former co-captain Keith Hernandez, for twice openly campaigning for the Mets’ managerial position while it was still occupied by incumbents Art Howe in 2004, and in 2008 Willie Randolph.

In 2008, he managed the Orange County Flyers of the Golden Baseball League, guiding his team to the GBL Championship and was named Manager of the Year.

In October 2009, Carter was named head baseball coach for the NCAA Division II Palm Beach Atlantic University Sailfish.

In May 2011, Carter was diagnosed with four malignant tumors in his brain after experiencing headaches and forgetfulness. Doctors confirmed that he had a grade IV primary brain tumor known as glioblastoma multiforme. Doctors said that the extremely aggressive cancer was inoperable and Carter would undergo other treatment methods to shrink his tumor. On January 20, 2012, daughter Kimmy posted on her blog that an MRI had revealed additional tumors on her father’s brain. Even as he battled an aggressive form of brain cancer, Carter did not miss Opening Day for the college baseball team he coached.

The 11th edition of the Merriam-Webster’s Collegiate Dictionary, published in 2012, credits Carter, who rarely used profanity, with the first recorded use of the term “f-bomb.”

Carter died on February 16, 2012, at the age of 57. Nine days later, the Mets announced that they were adding a memorial patch to their uniforms in Carter’s honor for the entire 2012 season. The patch features a black home plate with the number 8 and “KID” inscribed on it. On the Mets’ 2012 opening day, the Carter family unveiled a banner with a similar design on the center field wall of Citi Field.

The NHL’s Montreal Canadiens, who had purchased the Expos’ mascot Youppi! and hung retired numbers in its arena after the Expos’ relocation to Washington, paid tribute to Carter by presenting a video montage and observing a moment of silence before a game against the New Jersey Devils on February 20, 2012. All Canadiens players took to the ice during pre-game warm-ups wearing number 8 Carter jerseys, and Youppi! appeared wearing an Expos uniform. In addition, Youppi! wore a patch on his Canadiens jersey featuring a white circle with a blue number 8 inside it for the remainder of the season.

At Carter’s memorial service, on February 24, 2012, Expo teammate Tommy Hutton made note of Carter’s deep faith. The three loves in Carter’s life, Hutton said, were his family, baseball and God.

On March 28, 2014, during an exhibition game between the Toronto Blue Jays and the New York Mets at Olympic Stadium in Montreal, Quebec, a banner was unveiled in honor of Carter in a special ceremony before the first pitch. Carter’s widow Sandy and daughter Kimmy were present on field for an emotional video tribute and the unveiling of the banner on the outfield wall, which reads “Merci! Thank You!” and contains an image of a baseball overlaid with Carter’s retired number 8.