A system for overturning tanks, in particular tanks of kneading machines, includes a vertical supporting structure, an overturning unit, which is mobile along the structure between a lowered position and a raised position and can turn about an axis transverse to the vertical direction, and a system for driving the movement of said unit between said lowered position and said raised position. A further actuation system is provided for governing the movement of rotation of said unit independently of said movement between said lowered position and said raised position.