For both residential and commercial buildings, one of the largest portions of the total energy consumption and environmental impact lies within the heating and cooling of the building and the thermal inefficiencies of the building envelope. To meet the Paris Climate Agreement’s goal of reducing global warming by 2 degrees Celsius, the thermal efficiency of buildings should be increased by 30%. Phase Change Materials (PCMs) have been used in gypsum wallboard with great success but have not performed as well in concrete due to the resulting decrease in the concrete’s compressive strength and the survivability of the PCM during mixing and curing. Testing has shown that concrete walls containing PCMs consistently show a 3-degreesCelsius change in temperature compared to similar walls without PCM. This study aims to build upon previous work in the literature and further explore the effect of the water–cement ratio, aggregate content, and PCM content on the thermal and mechanical properties of PCM concrete. The PCM concrete used in the study was composed of Type I cement, silica fume, sand, and 24 degree Celsius microencapsulated dry PCM. The compressive strength of the concrete was measured at 7 days, and the compressive strength and thermal performance were measured at 28 days. The thermal performance was assessed using a radial heat flow method that involved recording the temperature rise in a cylindrical concrete specimen as it was heated using a cartridge heater.