Former Juventus and Croatia defender Tudor was appointed as successor to Jan Olde Riekerink in February but could only lead Gala to fourth place last season.
A 2-1 loss away to Yeni Malatyaspor on Sunday proved to be the 39-year-old's final game in charge, with that loss directly after an embarrassing cup defeat at second-tier Sivas Belediyespor, although Gala progressed to the next round on aggregate.
The 20-time champion sits second in the Super Lig table, a point behind leader Istanbul Basaksehir, but Tudor has paid the price for four defeats in their last seven league matches and for failing to get through the qualifying stages of the Europa League.
Tudor was criticised by Netherlands icon Wesley Sneijder after he left Istanbul in July.
"The coach made his choice," Sneijder said. "He made the choice not to work with me.
"If some coach doesn't want to work with you then you have to look for something else. If the coach doesn't want to use you anymore then you don't have a jersey number."