This work aimed to study the thermal and crystalline properties of poly (1,4-phenylene sulfide)@carbon char nanocomposites. Coagulation-processed nanocomposites of polyphenylene sulfide were prepared using the synthesized mesoporous nanocarbon of coconut shells as reinforcement. The mesoporous reinforcement was synthesized using a facile carbonization method. The investigation of the properties of nanocarbon was completed using SAP, XRD, and FESEM analysis. The research was further propagated via the synthesis of nanocomposites through the addition of characterized nanofiller into poly (1,4-phenylene sulfide) at five different combinations. The coagulation method was utilized for the nanocomposite formation. The obtained nanocomposite was analyzed using FTIR, TGA, DSC, and FESEM analysis. The BET surface area and average pore volume of the bio-carbon prepared from coconut shell residue were calculated to be 1517 m2/g and 2.51 nm, respectively. The addition of nanocarbon to poly (1,4-phenylene sulfide) led to an increase in thermal stability and crystallinity up to 6 loading of the filler. The lowest glass transition temperature was achieved at 6 doping of the filler into the polymer matrix. It was established that the thermal, morphological, and crystalline properties were tailored by synthesizing their nanocomposites with the mesoporous bio-nanocarbon obtained from coconut shells. There is a decline in the glass transition temperature from 126 °C to 117 °C using 6 filler. The measured crystallinity was decreased continuously, with the mixing of the filler exhibiting the incorporation of flexibility in the polymer. So, the loading of the filler into poly (1,4-phenylene sulfide) can be optimized to enhance its thermoplastic properties for surface applications. © 2023 by the authors.