Building energy efficiency is vital to achieve human thermal comfort with minimum energy consumption. It is a great concern in extremely hot countries such as Oman. This study aims to investigate the thermal performance of contemporary mosque buildings in comparison to traditional mosque buildings in Oman. The research methodology employs energy modelling using EDSL’s Tas Engineering computer simulation software. The analysis focused on how traditional mosque buildings compare to contemporary mosque buildings in terms of dry bulb air temperature and different thermal loads. The outcome showed the traditional mosque building design and construction are better suited for free-running buildings, while contemporary mosque building design and construction achieved less cooling load demand per area.