Los Angeles police Officer Joe Buscaino had the most votes in Tuesday's election with 29 percent.
Assemblyman Warren Furutani came in second with 22 percent of the vote. They'll now face off in a Jan. 17 runoff.
Hahn was elected to Congress in July, vacating the L.A. City Council's 15th district seat.
Mayor Antonio Villaraigosa announced his support for Furutani in mid-July. Furutani also received endorsements from a handful of labor unions representing government workers and the Teamsters, as well as the Los Angeles County Democratic Party.
Other candidates who appeared on the ballot were:
- Frank Pereyda, businessman
- Jayme Wilson, businessman, community leader
- Gordon Teuber, Hahn's economic director
- Justin I. Brimmer, Los Angeles legislative deputy
- Rebecca Chambliss, realtor
- Pat McOsker, firefighter/labor leader
- M. "Candice" Graham, community activist, businesswoman
- Rudy Svorinich Jr., small business owner
- John M. Delgado Jr., businessman
Four people also qualified as write-in candidates, including James T. Law, Timothy "Dream" Weaver, Robert Farrell and Emery D. Soos.
City News Service contributed to this report.