Natural bast fiber-incorporated polymer matrix composites assures the adequate replacement of conventional material to meet their future demand such as cost-effectiveness, lightweight, specific mechanical strength and high stiffness. Natural fiber-reinforced composites face higher moisture absorption, incompatibility, de-bonding and inadequate adhesion behavior. The novelty of this research work is to enhance the adhesion behavior and limit the moisture absorption capabilities by the additions of NaOH-treated hibiscus sabdariffa bast fiber with 25wt% in High-Density Polyethylene (HDPE) matrix and hybridize with the incorporation of 0wt%, 3wt%, 5wt% and 7wt% of silica nanoparticles by compression molding technique. The silica nanoparticles were derived from agricultural rice husk ash, sugarcane ash, and paddy straw through the acid precipitation technique. The composite density, surface morphology, water absorption, flexural strength and thermal absorption were evaluated and its experimental results showed significant improvement in characteristics. The composite density has been conforming to the additions of hibiscus sabdariffa bast fiber and SiO₂ nanoparticles. The morphology studies revealed uniform particle distribution with the effectiveness of bonding quality. The composite contained 25wt% of hibiscus sabdariffa bast fiber with 7wt% SiO₂ offered high flexural strength of 124.82 MPa, a low water absorption rate of 6.01% and low mass loss at a higher temperature.