<p>Volumetric behaviour of soil subjected to thermal cycles governs soil deformation which affects water permeability and shear strength of soil. It is vital for evaluating the performance of earthen structures, especially under climate change. However, the apparatuses developed for investigating such behaviour can induce significant measurement errors. This study developed a simple thermal oedometer equipped with a silicone-rubber heater and a thermoelectric cooler. To demonstrate the capability, the oedometer deformation under different vertical stresses and thermal cycles was determined. The thermal deformation of kaolin clay with two replicates was also examined. Results reveal that the new oedometer responded elastically to temperature changes, regardless of vertical stress applied. The oedometer deformation also showed negligible hysteresis caused by heating and cooling paths and the number of thermal cycles. Compared with some existing apparatuses, the maximum hysteresis in the oedometer deformation due to heating and cooling was reduced by 90%. Furthermore, the variation of clay deformation with thermal cycles was qualitatively consistent with that reported in literature. The deformation difference between the two replicates after heating and cooling was also close to the accuracy of the oedometer, demonstrating that the measurements obtained by the new oedometer are repeatable. The present study provides a new, simple method using thermoelectricity for investigating volumetric soil behaviour under thermal cycles, which can help to improve the performance of earthen structures against climate change.</p>