Haines first became known in the 1930s as an actor on the radio crime series Gangbusters. Four decades later, he would return to radio, starring in many episodes of the CBS Radio Mystery Theater.
His best known role was that of next door neighbor Stu Bergman on the soap operaSearch for Tomorrow. He joined the show for its eleventh episode in 1951, and remained on the serial for the show's duration. In this role, which he played from 1951 to 1986, Haines became very popular. He won Daytime Emmy Awards in 1976 and 1981, and was First LadyPat Nixon's favorite soap opera actor. Haines was reunited with Stuart on the prime-time special which saluted 50 years of the soaps in 1996.
In the 1980s, he co-starred with one of his Search for Tomorrow co-stars, Rick Lohman (who had played his grandson, Gary Walton) in a short-lived sitcom, called Phyl and Mikhy. Larry played Max Wilson, the father of Phyllis Wilson Orloff (Murphy Cross), who was married to Mikhy Orloff.
In 1989, several years fter the cancellation of Search for Tomorrow, he briefly joined the cast of another NBC/Procter and Gamble serial, Another World. Larry played the role of Sid Sugarman, Ada Hobson's old boyfriend who escorted her to a gala honoring the show's 25th anniversary. He was later in the cast of Agnes Nixon's Loving., playing Neal Warren, the biological father of Gwyneth Alden whom he reunited with right before she was identified as the serial killer in the slaying of the Alden family and several other characters. In the last episides of the show, his character proposed to old girlfriend Kate Rescott.
Haines died on July 17, 2008. He was predeceased by his former wives, Gertrude Haines and Jean Pearlman Haines as well as by his only daughter, Debora Haines.