An integrated flow rate control valve assembly is provided between an engine and a radiator. The integrated flow rate control valve assembly includes a housing in which a plurality of valve rooms separated by partition walls are formed and a plurality of rotary valves provided in the plurality of valve rooms, respectively, and an engine cooling system including the same, and according to the present disclosure, a sealing between cooling water lines is fundamentally solved, thereby enabling cooling water leakage prevention and structural robustness.