Natural plant fiber/agricultural waste materials have potential in composites due to their eco-friendliness, low cost and sustainability. Plastic and agro-wastes dumping are threatening concerns that must be settled for the protection of the worldwide ecosystem. In this study, the physical and mechanical properties of rice husk flour (RHF), corncob flour (CCF), walnut shell flour (WSF) and wood flour (WF) agro-waste filled recycled high density polyethylene biocomposites were investigated. Results showed bulk densities of RHF 350 kg/m3, CCF 310 kg/m3, WSF 400 kg/m3 and WF 250 kg/m3. Results showed moisture content of RHF 7%, WSF 6.4%, CCF 6% and WF 8%. Particle size distribution of 60-100 mesh size of the fillers was 0.295 mm to˂0.125 mm. Results showed that WF composite showed higher flexural modulus of 3.0 GPa and impact strength of 60 J/m followed by RHF with flexural modulus of 2.75 GPa and WSF with impact strength of 54.4 J/m compared to the control sample of 1.75 GPa and 38 J/m. The flexural strength of WF composite was 27.4 MPa followed by RHF composite 25.4 GPa, CCF composite 20.1 GPa and WSF composite 18.1 GPa compared to the control sample of 30.5 GPa. The higher bulk densities of RHF, WSF and CCF resulted in fiber accumulation at some parts of the composite, thereby causing weak points and the resultant lower mechanical properties compared to WF composites with lower bulk density. The study has shown that agro-waste fillers could be used in composite production with good results compared to WF composites.