Obama will be joined Sunday by U.S. Senate candidate Joe Sestak and gubernatorial candidate Dan Onorato. The rally is at a park next to Robert Fulton Elementary School in the city's Germantown section.
Democratic organizers say it's Obama's first public political event in Pennsylvania since he's been in office.
Obama was in Philadelphia twice in the past month, once to appear at a private fundraiser for U.S. Senate candidate Joe Sestak and once to deliver an annual back-to-school presidential pep talk.
Philadelphia is a friendly environment for Obama, with four in five voters there registered as Democrats.
The election is Nov. 2.