This paper presents a laboratory study on the properties of rice husk ash (RHA) cement composite mortars incorporating nano-SiO2. Different amounts of nano-SiO2 (0%, 1%, 3% and 5%) were incorporated into the mortars with 20% replacement of RHA. The compressive and flexural strengths of mortars were tested at 7, 28, 60 and 90 days. The water absorption test carried out at 28 days. The drying shrinkage of mortars was measured up to the age of 42 days. Scanning electron microscopy (SEM) observation also conducted to evaluate the effect of nano-SiO2 on microstructure of cement paste containing RHA. Incorporating nano-SiO2 into RHA mortars significantly improved the mechanical strength and water absorption properties of the products. Nano-SiO2 increased the drying shrinkage of RHA mortars. SEM analysis showed that nano-SiO2 improved the microstructure of RHA pastes on dense and compact form.