A reduction gear assembly (1a, 1b), particularly for the transmission of high power levels, comprising at least one driving shaft (2) and at least one driven shaft (4), which are kinematically connected to each other by transmission means (5a, 5b) and are mutually non-coaxial. The transmission means (5a, 5b) comprise at least one first kinematic chain and at least one second kinematic chain, which are parallel to each other and have the same transmission ratio. More specifically, between the driving shaft (2) and the kinematic chains torque distribution means (7a, 7b) are interposed which are adapted to distribute the power that can be transmitted from the driving shaft (2) to the driven shaft (4) partly through the first kinematic chain and partly through the second kinematic chain. Moreover, the transmission means (5a, 5b) comprising a single driven gear (6), which is keyed onto the driven shaft (4) and is kinematically connected to the kinematic chains.
