This study investigates the impact of the characteristic of palm shells on mechanical properties of biomass concrete. Seven types of concrete were made, six of those concretes are composed of substitutions with different proportions of palm nut shells and one formulated type served as a control concrete. The variation of mechanical properties of these concretes according to the curing time was studied. The research findings indicate that mechanical properties of the specimens increase with curing time. However, the substitution of palm nut shell in concrete leads to a decrease in the mechanical properties of concrete. these properties decrease with increasing substitution percentage. Furthermore, the splitting tensile strength measured at twenty-eight days is 2.05 MPa (control concrete) and drops to 1.08 MPa for 20% crushed shells then decreases to 0.44 MPa for 100% of whole shell. The flexural strength decreases with the increase in the proportion of shell. This study highlights the potential for integrating palm nut shells into concrete.