An integrated heat exchanger and coolant reservoir includes a reservoir structure that extends in a length direction from one end to an opposite end. A coolant inlet is arranged at one of the ends, and a coolant outlet is arranged at one of the ends. Coolant volumes extend in parallel along the length direction, and are fluidly connected in series to define a coolant flow path between the coolant inlet and the coolant outlet. An internal structure arranged within the reservoir structure has walls that separate individual coolant volumes from one another. Refrigerant flow paths are provided within at least one of the walls.