Maguire and DiCaprio filed suit against John Schindler, a man identified as a director and line producer on "Don's Plum," an independent film shot but never released in the United States.
Maguire and DiCaprio claim they agreed to make short film in order to help their friends' careers by giving them a chance to get screen credit when it was shown at film festivals, court documents said.
After "Titanic" catapulted DiCaprio to stardom, Schindler and a "Don's Plum" actor, R.D. Robb, allegedly wanted to release the project as a full-length film, which Maguire and DiCaprio said was never the deal.
The parties reached a confidential agreement, allowing for the film to play only in Europe.
The actors allege Schindler again wants to exploit the film for his own purposes.