Warren brought in 59 percent of the vote compared to Richards' 41 percent. The vote means Warren will have the Democratic spot on the November ballot. She will face Green Party candidate Alex White. Richards also has third party lines, but has not said if he will actively campaign. There is no GOP candidate.
The Democratic primary for mayor is important because Democrats have a 6 to 1 enrollment edge over Republicans in the city.
Warren's win is considered a monumental upset because she was outspent and Richards is the incumbent and party-backed candidate.
Warren, 36, is a lawyer who has spent her career working for Assemblyman David Gantt.
If Warren wins the November election, she will become Rochester's first female mayor.