The 'Milk' actor - who has been assisting in the country's relief efforts since it was struck by a devastating earthquake two years ago - was offered the position by the nation's foreign minister Laurent Lamothe while at the Cinema for Peace benefit in Los Angeles on Saturday night.
Picking up a humanitarian award for his work in Haiti, he told the crowd: "I do accept [the job]," before adding it would be nice to be "called, 'Hey Mr. Ambassador.' "
The event raised $5 million for the troubled country, with an auction taking place which saw Damien Rice spend $475,000 on a guitar owned by Bono and Julia Roberts' husband Danny Moder placing a $50,000 bid on a trip to Hawaii with Sean.
Other celebrities who attended the event included Demi Moore - who took along daughter Rumer - Mel Gibson, Kim Kardashian, Hilary Swank, Orlando Bloom, George Clooney and James Gandolfini.
US Secretary of State Hillary Clinton also made an appearance at the Montague Hotel in Beverly Hills.