The Cassini spacecraft, NASA's mission to investigate the Saturn system, has undergone a system-level thermal balance test program to permit verification of the science instrument thermal designs in the simulated worst-case environments. Additionally, other objectives such as functional checkout, collection of thermal data for analytical model adjustment, and flight temperature transducer verification were also attained. In the interest of cost and schedule, transient off-sunpoint conditions were not tested.The test demonstrated that the required system resources such as heater power and radiator area were adequate. In the instance of the Cosmic Dust Analyzer, allowable flight temperature limits were violated, but this problem is being addressed without a significant impact to system resources or thermal design robustness. Finally, the thermal acceptability of a black Kapton “sock” was demonstrated for the magnetometer boom.