Pitt, who co-starred with Cruise in the 1994 film "Interview with the Vampire," was said to have made the remark while promoting his new World War II movie "Inglourious Basterds."
Cruise's 2008 film was based on the true story of a botched attempt to assassinate German dictator and Holocaust architect Adolf Hitler.
Rottentomatoes.com indicated both of Pitt's and Cruise's WWII movies earned generally favorable reviews.
Asked by a Stern journalist for his opinion about "Valkyrie," Pitt reportedly said, "It was a ridiculous movie."
However, Pitt's manager told People.com the report was "inaccurate," adding, "Brad has never even seen 'Valkyrie.'"