The marine pollution of plastic wastes is one of the severe impacts of the human activities on the planet. Main treatments of plastic wastes include landfilling and incineration with or without energy recovery. A sustainable management is transforming such wastes into value-added products. This study aims to reinforce recycled plastics with unusable agricultural wastes so to meet requirements of added value use of recycled plastics. In this study, recycled polystyrene (R-PS) is reinforced with cottonseed hulls (CS-H). Beyond 30 %wt content, the non-adhesion of fillers to the plastic acts likely as a high porosity and decreases the tensile resistance of R-PS. Regardless of the content of CS-H fillers, the addition of these increases the Young modulus of R-PS (from 1600 MPa up to 3600 MPa at 20% wt of CS-H content) and decreases it impact resistance by -20% (the peak impact force decreases from 1 KN to 0,8 KN and the absorbed energy from 2,72 J to 2,25 J).