Enhancing thermal properties of concrete blocks in hot climates is crucial for energy efficiency. In this study, the thermal properties of wax-expanded polystyrene (EPS) composite insulation were investigated to assess its effectiveness in reducing heat transfer and improving heat capacitance. Four hollow concrete blocks, measuring 10 cm × 19 cm × 40 cm were examined: three blocks were filled with varying ratios of wax and Expanded Polystyrene, and one remained hollow as a control. The specific heat capacity of the wax-Expanded Polystyrene composite was measured to evaluate its thermal storage potential. Additionally, the thermal insulation abilities of the filled blocks were assessed using a heat source and a thermal camera. The results showed that the blocks with the wax-EPS composites exhibited reduced heat transfer compared to the control block, demonstrating improved thermal performance. The block with the higher wax content additionally displayed greater specific heat capacity, achieving a value of 1825.1 (J/kg.K), indicating enhanced thermal storage capabilities. These findings highlight the potential of wax-EPS concrete blocks in improving thermal regulation, contributing to a viable and energy-efficient building material for hot climates.