Economic and population growth in developing countries, combined with local and global warming, are primary factors in exacerbating the cooling demands by the population. Currently, energy consumption from buildings account for 36% of global energy demand and a staggering 90% in Kuwait. Electricity demand is expected to continue to rise and becomes problematic in countries that are highly dependent on the oil and gas industry for energy production. This ongoing situation underscores the importance of implementing sustainable solutions, such as, passive cooling with phase change materials (PCMs), to improve indoor climates and reduce energy consumption. This study aims to contribute to the field by experimentally utilizing and analyzing the impact of commercially available PCMs on indoor passive cooling. Two identical 75-mm sandwich panel cabins were constructed in Kuwait —one serving as a control and the other as an experimental cabin. Both cabins were equipped with sensors to measure the indoor temperature and a weather station to monitor outdoor temperature. PCM was added incrementally over several weeks. Results demonstrated that the use of PCM significantly reduced indoor temperature fluctuations and peak temperatures in the experimental cabin compared to the control cabin. Applying PCM to all four walls reduced the maximum temperature by 4.25 °C. The findings indicate that PCM can effectively moderate indoor temperatures, maintaining a more stable and comfortable indoor climate without the need for mechanical cooling systems. This study highlights the potential of PCM as a sustainable solution for reducing energy consumption in hot climates, particularly in regions heavily reliant on air conditioning.