The Frenchman played for the Dutchman at Bayern Munich, where they won a league and cup double in his first season in 2009/10.
Ribery acknowledges that Van Gaal brought on-pitch results but has questioned his man-management skills.
“We had problems on a human basis,” Ribery told Goal. “When he started, nobody knew what was going to happen.
“His idea was that he did not care about names at all, you don’t need stars, everybody had to prove themselves again.
“The first contact with him was already poisoned. As a professional you lose your trust. He does great things on the pitch but the coach Van Gaal was a bad man. Our relationship was crushed.”