In an interview on Access Hollywood Live, Sheen said the actors will be heading for Port-au-Prince in about two weeks.
"And I'm excited as hell because, you know, if I can bring the attention of the world down there, then clearly this tsunami keeps cresting," he said.
Penn, who won an Oscar for "Milk" a couple of years ago, began working on Haitian relief soon after the earthquake in January 2010. He has been to the country many times since then.
In an interview for the April issue of GQ, Penn, who used to have a bad-boy reputation, defended Sheen: "When you divorce the moral judgments, which I prefer to do, I see a guy who has a clearer view of the nature of the world around him than is sometimes comfortable to have. Those are the sort of people who have a tendency to find altered states."