The effect of temperature variation has not been adequately addressed in the stress analysis of ancient stupas. However thermal loading is a significant contributor among the stresses acting on the stupa shell. This paper discusses the behaviour of one of the ancient stupas: Jethawana stupa under thermal loadings. Evaluation of properties of the stupa restoration brick such as water absorption and compressive strength were evaluated with adequate laboratory testing. Test results indicated that the restoration brick of the Jethawana stupa which was made akin to the original ancient stupa has higher quality than the modern bricks. Two-dimensional finite element model analysis using SAP2000 general purpose software package, was carried out to assess the stresses developed in the stupa surface due to the thermal loading effect. The said model analysis was conducted for five separate temperature load cases considering stress and deformation under thermal loading. The results showed that the compressive stresses had developed on the surface of the stupa than towards the core of stupa. Further, the stresses due to the thermal loading on the surface of the existing stupa were significantly higher at the juncture where the dome and the square chamber meet. When comparing the contrasting difference between the colour contours at the said location, it is evident that the result is significant. Even though the abnormal result does not lead to conclude that there is a definite impact of thermal stress on the existing restoration works, the study suggests that it could be taken as a notable point to do further analysis on the same area of study.