This study investigated the effect of spear grass fibre inclusion on the physical and mechanical properties of cement-bonded particle boards. Cement-bonded particle boards of 8 mm in thickness were manufactured using spear grass (Imperata cylidrica) and sawdust at different levels of cement mixing ratios of 2:1 and 3:1 and blending proportions of 100-0, 90-10, 80-20, 70-30 and 0-100% spear grass to sawdust respectively. The effect of the spear grass fibres inclusion was tested on Water Absorption, Thickness Swelling, Linear Expansion, and also on the mechanical properties such as Modulus of Elasticity and Modulus of Rupture of the cement bonded particle board produced. Value obtained for physical properties ranged from 16.83 to 80.42, 0.71 to 20.35 and 0.72 to 2.67% for Water Absorption, Thickness Swelling and Linear Expansion respectively. The value of mechanical properties ranged from 115.6935 to 541.8375 and 25908.26 to 160529.4N/mm2 for mixing ratio 2:1. 10560.8 to 153969.8 and 67.75 to 456.64 N/mm2 were recorded for mixing ratio 3:1 for Modulus of Elasticity and Modulus of Rupture respectively. The best materials mixture was found for 100:0, while 0:100 blending proportion constitute the weakest mixture. However, 90:10 proved spear grass inclusion was effective due to its close values with 100:0 blending proportion. The values for water absorption, thickness swelling and linear expansion showed that, after 24, 48, and 72 hours water immersion, there was increase in the physical properties as a result of decrease in both blending proportions and mixing ratios. The increase in physical properties was due to the reduction of the sawdust in the blending proportions and mixing ratios. MOE and MOR decreases with decreased in the blending proportion. The study has shown that spear grass can be utilized to produce cement bonded particle board but only at specified proportions.