The present research aims to evaluate the influence of adding silica nanoparticles derived from sugarcane bagasse, synthesized in the laboratory using the sol-gel method, on the properties of cement mortar in both its fresh and hardened states. In the fresh state, the study examines workability, consistency, and flow, while in the hardened state, it evaluates compressive strength and hydrophobicity. Specimens were prepared using Type N and Type HS cement, with the addition of nano-silica particles at 0.25%, 0.50%, 0.75%, 1.00%, and 1.50% by weight as a replacement for cement in the control mortar. The results revealed that 0.25% nano-silica was the optimal addition percentage for both mortars. Moreover, it was found that both fresh and hardened properties were negatively affected as the percentage of nano-silica increased. The compressive strength increased by 9% at 28 days and 12% at 56 days for the Type N cement mortar, while for the Type HS cement mortar, the strength increase was 9% at 28 days, 10% at 56 days, and 5% at 90 days. The contact angle test indicated that nano-silica particles reduce the permeability of the mortars, with specimens made with Type N cement exhibiting greater impermeability compared to those made with Type HS cement.