This study investigated the Brinell hardness of epoxy composites reinforced with cassava-cortex fibres and cow-bone particles using an 18-run Taguchi experimental design. Reinforcement composition, sodium hydroxide treatment and particle size were varied systematically. Hardness was measured on three specimens per formulation, and the mean values were analysed using factor-response comparisons, analysis of variance and categorical regression. Mean hardness ranged from 21 to 43 BHN, with the highest value recorded for RDT4PS100, containing 20 vol.% cassava cortex and 20 vol.% cow bone. Reinforcement composition produced the largest variation in the observed response. Treatment and particle-size effects were more difficult to separate because their experimental assignments overlapped. The findings demonstrate the potential of the balanced hybrid formulation for further mechanical and application-specific evaluation.