Abel Ferrara told French daily Le Monde that he has cast Depardieu alongside French actress Isabelle Adjani, who will play Strauss-Kahn's journalist wife Anne Sinclair.
Ferrara told the newspaper he met Depardieu in September at the film festival in Deauville, where Ferrara screened the French premiere of his film 4:44 Last Day on Earth.
"He's great," he told Le Monde. "He's everything a film maker could want in an actor."
The script has already been written, based on what has been reported as well as his own sources. "I have my own detectives," he said.
Dominique Strauss-Kahn was forced to resign as head of the International Monetary Fund after he was arrested in New York following accusations of sexual assault by a hotel maid. The charges were later dropped.
Strauss-Kahn remains dogged by scandal in France, although charges by a journalist against him were also dropped.
Ferrara said the film will be a work of fiction rather than a blow-by-blow account of what happened.
"This will be a film about politics and sex," he said. The movie will be shot in New York, Washington and France.
The film's likely producer, Vincent Maraval, was reluctant to discuss details of filming, but Ferrara was less restrained.
"Vincent doesn't want to talk about the project, that's normal, he's the producer," said Ferrara. "But I'm the director! Noone can stop me from talking about my movie."