The film, about a drunk playboy set to inherit a fortune, failed at the box office besides being panned by the critics, the Sun reported online.
"I didn't know a lot about script construction. I know more now. I was just embracing things enthusiastically. I thought I could do anything," the 37-year-old said.
The comedian, who is famous for taking digs at famous people, admitted that he was hurt by the harsh criticism of the movie.
"I felt a little bit bruised. I felt I'd made a mistake."
Apart from Brand, the film starred Helen Mirren, Jennifer Garner and Greta Gerwig.