Lawyer David Koubbi told The Associated Press that Tristane Banon will file the suit Tuesday in Paris.
Banon has described an encounter several years ago in which Strauss-Kahn allegedly assaulted her.
Strauss-Kahn was arrested in New York in May on charges that he tried to rape a hotel maid. Strauss-Kahn, who denied wrongdoing, was released without bail last week after questions emerged about the maid’s credibility.
Koubbi had said in the past that they would not file a lawsuit until the American trial was finished. He said Monday that they had decided to move forward now instead of waiting.