She has represented California in the House of Representatives

Pelosi started climbing the Democratic political ladder after relocating to San Francisco and making friends with Phillip Burton, a congressman from the 5th district. Sala Burton, who won a special election in 1983, succeeded her late husband Phillip Burton after his death in 1983. 2 more elections were won by Sala Burton (in 1984 and 1986). Burton opted not to seek reelection in 1988 after being diagnosed with cancer in the latter part of 1986. Pelosi was chosen by her as her chosen replacement, securing for her the backing of the Burtons' contacts. Just one month after taking the oath of office for his second full term, Burton passed away on February 1, 1987. Pelosi won the special election to succeed her, defeating Republican Harriet Ross in a runoff on June 2 and Democratic San Francisco supervisor Harry Britt on April 7, 1987. A week later, Pelosi was inaugurated.

Since she won, San Francisco, California, has been represented in Congress as a safe Democratic district. She represents the 12th congressional district of California, which includes the majority of San Francisco's city and county. Pelosi served as a representative for the 5th district from 1987 to 1993; from 1993 to 2013, she served as a representative for the 8th district after new district lines were set in the wake of the 1990 census.

Republicans, who currently make up barely 13 percent of the district's registered voters, have not made a serious run for the seat since the early 1960s, and Democrats have held the seat since 1949. She was reelected in the 1988 general election and has since been re-elected 16 more times with no significant challengers, winning with an average of 80% of the vote each time.