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.
Where does the term “the luck of the Irish” come from?