Sieroty has spent much of his career in public service. He was elected to the California State Assembly in 1966, serving until 1977, when he was elected to the state Senate. Sieroty retired from the state legislature in 1982. While in the legislature, Sieroty authored more than 100 bills, including the California Coastal Protection Act , the California Financial Privacy Act, the Dymally-Sieroty Children's Center Construction Act and the Art in Public Buildings Act. Prior to his term in the state legislature, Sieroty served as deputy director of the Chile-California Program and was executive secretary to Lt. Gov. Glenn Anderson from 1961 to 1965. He is a founder of the Progressive Jewish Alliance. Sieroty, whose father Julian was a USC graduate, is the chairman of the Sieroty Company, which was founded by his grandfather in the 1890s as Eastern-Columbia retailer of clothing and accessories. The Eastern-Columbia building remains at the corner of 9th Street and Broadway in downtown Los Angeles. The landmark is decorated with turquoise terracotta tiles, making it one of the signature Art Deco buildings in Los Angeles.