Low Earth Orbit (LEO) satellites rely on robust and efficient communication systems to enable telemetry, tracking, command (TT&C), and data transmission. Among the various frequency bands used for satellite communication, the S-band (2–4 GHz) is widely favoured due to its favourable propagation characteristics, resistance to atmospheric attenuation, and moderate bandwidth availability. The performance of S-band transceivers is influenced by multiple factors, including power efficiency, modulation schemes, antenna design, and resilience to spaceborne environmental effects such as temperature variations and radiation exposure. This paper presents a thermal analysis case study of an S-band transceiver from an ongoing KACST Low Earth Orbit (LEO) mission to ensure the system operates within its designated temperature range. The study investigates the thermal behaviour of the transceiver in space, considering factors such as solar radiation, internal heat dissipation, and orbital conditions. The results provide insights into the thermal design considerations necessary to enhance the operational stability of S-band transceivers in LEO satellites. Mathematical modelling and numerical simulations are carried out using Finite Element Modeling and Analysis (FEMAP). Different thermal cases, including the worst hot case, the worst cold case, and the nominal case are simulated. The results show that the minimum and maximum temperatures experienced by the S-band transceiver during orbital operation are 15.87 and 40.30 ℃, respectively, with a nominal range between 21.80 ℃ and 29 ℃ °C. Finally, the predicted nominal temperatures are compared with in-orbit measured results, ranging from 29.56 ℃ to 32.38 ℃. The nominal real-time measurements from the transceiver of the ongoing mission fall within the predicted temperature range, validating the design and confirming that the temperature range is acceptable for operation.