This study was carried out to develop empirical models for predicting the mechanical properties of injection moulded polypropylene-grass composite. The two screw plunger injection moulding machine with maximum clamping force of 70 tons and shot capacity of 3.0oz was used to produce Polypropylene-Grass composite at barrel temperature which ranged from 210^oC to 310^oC. The mechanical properties obtained from the experimental investigation of the produced polypropylene-grass composite were used to develop the empirical models for tensile strength, proof stress, percentage elongation and flexural strength respectively. The developed models were validated using coefficient of determination (R²) and mean absolute percentage error (MAPE). The coefficient of determination obtained ranged from 0.9213 (92.13%) to 0.9911 (99.11%) which indicates that a substantial good fit was achieved by the models developed. The mean absolute percentage error of the developed models ranged from 0.12% to 6.53% which was below 10% recommended. The values obtained from the validation of these models were therefore found to be satisfactory and shows good predictability of the models.