A stacked busbar assembly includes two or more busbar subassemblies, each including a plurality of busbars having one or more power semiconductor devices bonded thereto (e.g., IGBTs, power diodes, and the like). Each busbar has an internal integrated cooling system including one or more fluid channels in communication with an inlet and an outlet. The busbar assemblies are stacked such that their respective inlets and outlets are aligned and a coolant may then flow in parallel therethrough.