The present scenario forces researchers to reduce raw material usage for future conservation and imposes a responsibility to reuse the waste by converting it into valuable products. With a state of potential, the components are put forward for reusing the diamond-cutting waste as effective filler particles in the polyepoxide-glass laminated hybrid composite. The polymer composites were prepared using the hand lay-up process under hydraulic loading conditions. The composites were formulated by changing the diamond filler fraction (1, 3, 5 and 10 wt%) and keeping a constant glass weight percentage of 20%. The composite’s mechanical, thermal stability and erosion properties were evaluated to study the effect of diamond filler material in glass fibre composites. With the addition of 5% diamond particles, the tensile, flexural, and Shore D hardness were improved by a maximum of 48, 34 and 26%, respectively, compared to the polyepoxide glass fibre composite, due to the restraint on deformation of polymer chains. There was minor diamond particle aggregation due to fines in more than 5% of the diamond filler, reducing the rate of improvement of the mechanical behaviour. The higher thermal conductivity and increased strength offered by diamond filler improved thermal resistance and slowed down the thermal degradation of composites. The sand erosion test reveals that diamond particles boosted the erosive wear resistance of the composites by offering high mechanical strength, which could change the erosion wear mechanism. Erosion morphology determined through SEM analysis found that high-volume diamond particles reduced erodent-polymer matrix interaction at the micro level, decreasing the erosion wear of diamond-filled composites.