Williams was born in Plainfield, New Jersey, and graduated from Oberlin College in 1941. He engaged in newspaper work in Washington, D.C., and studied at the Edmund A. Walsh School of Foreign Service of Georgetown University until called to active duty as a seaman in the United States Naval Reserve in 1941. He became a naval aviator and was discharged as a lieutenant, junior grade, in 1945. After being employed in the steel industry for a short time, he graduated from Columbia Law School in 1948, and was admitted to the bar and commenced practice in New Hampshire. He returned to Plainfield in 1949 and continued to practice law, and was an unsuccessful candidate for the New Jersey General Assembly in 1951 and for city councilman in 1952.

Williams was elected to the House of Representatives in a special election in 1953, and was re-elected in 1954 but defeated for re-election in 1956. He was elected to the Senate in 1958 and re-elected in 1964, 1970 and 1976, defeating a future leader in the Republican Party, David A. Norcross.

He also helped pass legislation that created the Occupational Safety and Health Administration and had a major role in passage of the Urban Mass Transportation Act of 1964, the first federal law to provide mass transportation assistance to states and cities. He also was the chairman of the United States Senate Special Committee on Aging from 1967 through 1971.

The Metropark train station had been renamed Harrison A. Williams Metropark Station in 1979, in recognition of his support for its construction. However, the name was removed from the station after his conviction.

In 1981, Williams, a resident of Westfield, New Jersey, at the time, was convicted of bribery and conspiracy in the Abscam scandal for taking bribes in a sting operation by the Federal Bureau of Investigation (FBI). The Senate Committee on Ethics recommended that Williams be expelled because of his “ethically repugnant” conduct. Prior to a Senate vote on his expulsion, Williams resigned on March 11, 1982. Sentenced to three years, he served two years in Federal prison as Inmate #06089-050, the first time in over 80 years that a senator had spent time in prison. Williams was also charged a $50,000 fine in addition to prison time. Released on January 31, 1986, he served the remainder of his sentence at the Integrity House halfway house, where he later became a member of the board of directors until his death on November 17, 2001. He also attempted to receive a presidential pardon from President Bill Clinton, but his request was denied.

Williams died of cancer and heart ailments at St. Clare’s Hospital in Denville, New Jersey, on November 17, 2001. He was a resident of Bedminster Township, New Jersey.