This study explores the effect of direct incorporation of different ratios of naphthalene with soil into concrete used in Mafraq-Jordan on thermal conductivity of concrete mixtures. The methodology depended on testing a number of 72 samples of concrete cubes. The base case samples were prepared only from a mixture of water, silica sand, and cement without additives. Additives of local soil and naphthalene of different ratios: 2.5%, 5%, 7%, 10% and 15%, were added to the tested samples. The samples were classified into two groups in terms of size and dimensions; 36 cubes with 5cm×5cm×5cm were tested for only thermal conductivity, and 36 cubes with 3cm×3cm×3cm were tested for compressive strength and thermal conductivity. All samples were tested after 28 days of casting according to the concrete standards. The results show that adding naphthalene and soil to the cementitious mixtures substantially decreases the thermal conductivity of concrete elements. A reasonable reduction in thermal conductivity was achieved compared with the base case samples. However, the compressive strength of samples remained within the acceptable values from the stand point of structural engineering. This enhancement in the thermal properties of concrete can be applied on building systems as concrete blocks used in internal and external walls.