Green composites using thermoplastics and thermosets got immense popularity long back when it newly introduced to the industry due to diminishing reliance on oil-based or gasoline materials, which causes numerous environmental problems. In this paper, bio-composites mechanical, chemical, thermal, and degradation properties of hybrid jute and coir fibers reinforced polylactic acid (PLA) investigated. Throughout the fabrication procedure of biocomposites, jute, and coir fibers characterized into three different categories raw, alkali-peroxide, and alkali-silane combined chemical treatments followed a design containing in a total of ten optimized samples. Jute and coir fibers were mixed with a solution of polycaprolactone (PCL) for better fiber-matrix adhesion prior to fabrication. The mechanical properties of alkali-silane treated reinforced fibers biocomposites improved compared to untreated fibers, which exhibited for fiber contents 40% an increase of respectively 32.8% by tensile strength 25.95% by tensile modulus, 24.58% by flexural strength, 23.64% by flexural modulus, and 26.08% by impact strength. Besides, moisture absorption, thickness swelling, thermal stability (TG), and surface chemistry analysis (FTIR) properties investigated, according to fiber-matrix contents ratio, hot-pressing time, temperature, and pressure to identify the effect of biocomposites due to chemical treatments. Moreover, the fiber surface effect of chemical treatments and interfacial adhesion morphologies observed using SEM. Eventually, alkali-silane combined optimized samples demonstrated the most desirable result in every aspect. In addition, a 90 days burial degradation performed to see the degradation flow of the biocomposites.