Polymer-based composites are crucial in various engineering domains such as automobile, marine, and construction applications. Specifically, these composites have lower weight, good strength and enriched thermal qualities. This study mainly focuses on the epoxy hybrid composite preparation by using 5% of alkalization solution-treated bast fiber and silica nanoparticles via injection moulding, and final epoxy composites consist of alkalization-processed bast fiber of 20 wt% along with 0, 2, 4, and 6 wt% nanosilica particle. Testing was conducted based on the epoxy composite’s tensile, impact, and hardness behavior. 6 wt% silica with 20 wt% basalt fiber processed with alkali offers maximum tensile and impact strength of 136.5 ± 0.4 MPa and 7.61 ± 0.5 J/mm2 and hardness behavior of 71 ± 0.2 HV. The optimum behavior of a composite containing 20 wt% of alkalization-treated bast fiber with 6 wt% silica nanoparticles is recommended for lightweight and structural applications.