Disclosed are joint active thermal management (ATM) systems for electric-drive vehicles, control logic for operating such ATM systems, and electric-drive vehicles equipped with a joint ATM system for heating/cooling the powertrain's drive unit (DU) section, power electronics (PE) section, and rechargeable energy storage system (RESS) section. A disclosed active thermal management system includes a first coolant loop with fluid conduits fluidly connecting a first electronic heat exchanger and a first pump with the DU and PE sections. The ATM system also includes a second coolant loop with fluid conduits fluidly connecting a second electronic heat exchanger and a second pump with the RESS section. A coolant-to-coolant heat exchanger, which is fluidly connected to the first and second coolant loops, is operable to selectively transfer heat between the coolant fluid circulating in the first set of fluid conduits and the coolant fluid circulating in the second set of fluid conduits.