Clinton joined a group of her supporters for a town hall-style luncheon at Langer's Deli.
Clinton said he's giving Greuel his vote of confidence because he knows she can get the job done, having worked in his administration in the Department of Housing and Urban Development. He said he'd also like to see a woman lead Los Angeles.
"I think it'd be even better to have the first female mayor," Clinton said. "I have seen her get things done."
Greuel said she's the candidate to create jobs and reduce the city's high unemployment.
"I'm going to bring the qualities and the efforts that this gentleman taught me, and my mentor Tom Bradley, many years ago to lead Los Angeles forward," Greuel said.
Also Saturday, fellow mayoral candidate Eric Garcetti met with environmentalists at an Earth Day celebration along the Los Angeles River in Atwater Village.
"This isn't about out-of-town folks telling us how to vote," Garcetti said about Greuel's event. "I have a lot of respect for the people who have supported Mrs. Gruel, who've supported me, but this is our decision, each voter, looking at our records."
Garcetti said he's focused on continuing to rebuild the city's neighborhoods.
The candidates are scheduled to debate on ABC7 on May 10.
The runoff election takes place on May 21.