The film is a romance about aid workers in Liberia, reported Variety Online.
Penn, 55, brushed aside the bad reviews at a press conference.
"I stand by the film as it is, and everyone is going to be entitled to their response. I've finished the film so it's not a discussion I'd be of value to," he said.
The director was flanked by stars Javier Bardem, Charlize Theron, Jeno Reno and Jared Harris. Penn's agent Bryan Lourd was also on hand, sitting in the crowd.
"I am surrounded at this table by performances that I'd pay to see 100 times," he said.
