Abstract: In this article, flexible and rigid polyurethane (PU)/copper (Cu) composites are prepared via a simple and cost-effective solution casting process. The filler dispersion and chemical bonding of composites are investigated by SEM and FTIR techniques. The results showed the homogeneous dispersion of Cu microparticles. Furthermore, thermal properties are investigated using DMA, DSC, and thermal conductivity measurements. The maximum improvement in thermal conductivity for flexible and rigid PU composites is 24%, and 48%, respectively, as compared to their pure counterparts. The obtained thermal conductivity values are also compared and analyzed with the mechanical property model (Corans and Patel model) and found in good agreement with the output of the model. DMA results showed enhancement in the storage modulus with filler loading while the DSC results revealed the endothermic temperature did not significantly change with adding Cu filler in both flexible and rigid PU matrices. The mechanical properties of composites were studied using tensile and hardness (Shore A and Shore D) test. For flexible PU composites an improvement in tensile strength (43%), Young's modulus (111%), Shore A hardness (6%), Shore D hardness (27%) as compared to pure flexible PU. For rigid PU composites a reduction in tensile strength (23%), Young's modulus (32%), and an increase in Shore A hardness (3%), Shore D hardness (5%) as compared to pure rigid PU. As a result of the current study, TC of rigid PU is found doubly enhanced compared to flexible PU at the same filler concentration. Copper microparticles can act as active filler in both flexible and rigid PU matrices.