In this work, Mulberry Stems (MS) obtained as a by-product of sericulture have been used as reinforcement for Polypropylene (PP) composites intended for green building, furniture and automotive applications. Mulberry stems are lignocellulosic and are renewable and sustainable sources but remain unutilized and are usually discarded as waste by burning or burying. An attempt has been made to utilize mulberry stems as substitutes for commonly used non-biodegradable composites using a simple and clean fabrication technique. The effects of reinforcement percentage (80% to 95% w/w) of MS and density (0.5 g cm⁻³ to 1.25 g cm⁻³) of composites on the properties have been studied. Results revealed that, 90/10 (MS/PP w/w %) was the optimum ratio that provides highest mechanical strength. Increasing the density enhanced the strength, thermal insulation, sound transmission loss, water stability and flame retardancy. The 1.25 g cm⁻³, 90/10 ratio composite had a high sound transmission loss of 46.6 dB and thermal conductivity of 0.130 W/mK which is 70% lower than neat gypsum board used in false ceiling applications. The high insulation and sound barrier properties of mulberry stem based composites are due to the unique hollow morphology of MS which aids in efficient absorbtion and dissipation of the thermal energy and sound waves. Weight loss of MS/PP composite after soil burial test for 120 days varied between 8.9% and 31.4%. MS/PP composites could be potentially used as a green replacement for ply, particleboards, false ceiling, automotive parts and other applications.