The People for the Ethical Treatment of Animals said tens of thousands of votes were cast in this year's month-long poll on PETA.org.
Other sexy vegetarians in the running were Kristen Bell, Russell Brand, Emily Deschanel, Milo Ventimiglia, Casey Affleck, Abbie Cornish, Hayden Panettiere, Jason Schwartzman, Robin Quivers, Mos Def and Raja Bell.
"Soon after I (went vegan,) I saw some documentary footage of what happens in the factory farming of cow. ... It sealed the deal," Kiedis said in a statement.
"I am vegetarian so I don't have clothes, shoes or bags made from leather or suede or any animal products. .... I'm on a mission," Lewis added. "I am totally against animal cruelty."
Previous winners of PETA's "World's Sexiest Vegetarians" title include last year's winners -- Carrie Underwood and Kevin Eubanks -- as well as Prince, Natalie Portman, Shania Twain, Chris Martin, Andre 3000, Tobey Maguire, Josh Hartnett, Alicia Silverstone and Lauren Bush.