Oxfam America is teaming up with eBay for the fundraiser.
Fans can bid through Wednesday on the opportunity to meet Firth, an Oxfam ambassador, and attend a screening of "Tinker, Tailor, Soldier, Spy!," his new film based on the best-selling novel by John le Carre.
The winning bidder will get two tickets to the Dec. 6 premiere in Los Angeles and the premiere after-party at the Chateau Marmont, as well as luxury chauffeur service to and from the events.
One hundred percent of the proceeds will benefit Oxfam America, the organization said.
Firth won the Oscar for Best Actor for his work in the 2010 drama "The King's Speech." He is also known for his work in the TV miniseries "Pride & Prejudice," and the movies "Shakespeare in Love," "Bridget Jones's Diary" and "Love Actually."