The Attitude Determination and Control System (ADCS) plays a crucial role in ensuring the stability and accuracy of satellite orientation in the presence of external disturbance torques. ADCS is one of the satellite subsystems comprising a combination of actuators and sensors that work together to regulate and align the satellite according to the desired concept of operations. ADCS system relies on external references to determine the satellite’s angular orientation that is relative to a fixed inertial reference frame. It is important to note that each ADCS system is designed to fulfill the specific requirements of its parent satellite, resulting in unique configurations and capabilities. The design and implementation of an ADCS system necessitates careful consideration of the satellite’s operational needs and the external disturbances it will encounter. By effectively managing these factors, the ADCS system ensures the precision and stability of the satellite’s orientation throughout its mission lifespan. In the space environment, the satellite subsystems are exposed to solar radiation (heat flux) and heat generated from the satellite components. This paper presents a thermal analysis case study of ADCS from an ongoing KACST low-earth-orbit (LEO) mission to guarantee that the system is kept within the operating temperature range. Numerical simulation using finite element modeling and analysis (FEMAP) is used. Different thermal scenarios are simulated at nominal and extreme (cold and hot) conditions are considered. Results show that the minimum and maximum average temperatures experienced by the ADCS during orbital operation are 7.4 and 30.8 ℃, with a nominal range of 15 and 21.3 ℃, respectively. Finally, the nominal predicted results are compared with a measured in-orbit result, with ranging temperatures of 14.3 and 16.3 ℃. The ADCS nominal real-time measurements from the ongoing mission fall within the predicted, and as a result, the design accepted temperature range.