Williams, the youngest of three boys, was born in 1954 in Santa Monica, California,[4] to Doris May Moore and Canadian-born Frank Millar Blenkhorn, of English, Scottish, and German ancestry.

[5] Barry and siblings Craig and Scott Blenkhorn[4] grew up in Pacific Palisades, California, where actor Peter Graves was a neighbor.

He was tapped to play English con man Hannibal in 1984, who conspired with Holly Sutton Scorpio (Emma Samms) on the top-rated General Hospital.

In 1989, Williams was honored by the Young Artist Foundation with its Former Child Star "Lifetime Achievement" Award for his role as Greg Brady.

Williams has made multiple appearances as a paid featured dancer at the World's Largest Disco in Buffalo, New York.

Between 2001 and 2002, he played Manager Dean "The Machine" Strickland in 13 episodes of the sitcom, Hollywood 7, which featured the British pop group S Club 7.

Williams participated as a friend of one of the patients, Chyna, and explained to her during a group session how drinking had a negative impact on his own life and career.

Williams responded by filing a complaint with the National Labor Relations Board, arguing that the fine was illegal because he had resigned from the union in September 2000 before the tour began.

[18] Williams was reinstated by Actor's Equity as a member in good standing in 2005 after he unionized a non-Equity production of A Christmas Carol in late 2004.