The use of graphene derivatives in cementitious composites offers notable mechanical and durability enhancements but is hindered by high production costs and scalability challenges, prompting interest in sustainable alternatives. This study investigates date syrup-based graphene coated sand hybrid (i.e., denoted as D-GSH), a bio-derived graphene derivative synthesized from waste date syrup and dune sand, as an additive to enhance cement mortar performance. Cement mortars incorporating 0.25-1.0 % D-GSH by weight of cement were prepared and tested for flowability, density, mechanical strength, and water ingress resistance. Microstructural characteristics were evaluated using XRD, FTIR, SEM, and TGA. Results showed that D-GSH slightly reduced flowability but significantly improved fresh and hardened densities (up to 165 % and 40 %, respectively). At an optimal dosage of 0.75 %, compressive strength, axial compressive strength, and modulus of elasticity increased by up to 55 %, while 1.0 % dosage delivered the highest flexural strength, albeit with delayed early-age performance. Durability indicators-including water absorption, porosity, and water absorption coefficient-were substantially reduced, with 0.75 % D-GSH yielding the most pronounced improvements. Microstructural analyses confirmed that D-GSH enhances matrix densification, hydration, and crack-bridging capacity, though excessive dosages may induce agglomeration and localized weaknesses. These findings confirm the potential of D-GSH as a sustainable additive for advancing cement mortar performance.