In Malaysia's tropical climate, maintaining thermal comfort in mosques is challenging due to high temperatures and humidity. Mosque courtyard designs which often designed in various shape play a key role in natural ventilation, but there is limited research on how these shapes affect thermal comfort. Understanding the impact of courtyard design is essential for creating more comfortable mosque environments. This research aims to conduct a comparative analysis of thermal comfort in U and O-shaped courtyards within mosque designs. Thermal comfort is evaluated by analysing key environmental parameters, including air temperature, relative humidity, air velocity, and mean radiant temperature. Field data were collected over multiple days, and the results indicate that the O-shaped courtyard provides superior thermal comfort due to higher air velocity and lower relative humidity. Conversely, the U-shaped courtyard, while maintaining similar air temperature, suffers from reduced airflow, leading to a less comfortable environment. The findings highlight the significance of courtyard design in enhancing thermal comfort through improved natural ventilation and reduced heat retention. The present study offers valuable insights into the architectural design of mosques in tropical regions, with a particular focus on the significance of courtyard forms in enhancing the comfort of internal spaces.