This study focuses on converting Plum Kernel Shell (PKS) waste biomass into biodiesel using a novel synthesized heterogeneous catalyst, contributing to the pursuit of renewable fuel from sustainable resources. Plum Kernel Shell (PKS) is waste biomass generated from plum fruit and available abundantly; utilizing it can help in many ways, such as overcoming environmental issues and promoting a circular economy. The precursor for the heterogeneous catalyst is derived from post-oil extraction waste biomass and further modified with metallic oxides (CuO and Mo) due to its acidic nature to enhance its efficacy for biodiesel production. Thorough characterization of the synthesized catalyst was conducted using analytical techniques such as XRD (X-ray diffraction), SEM (Scanning Electron Microscopy), EDS (Energy-Dispersive X-ray Spectroscopy), BET (Brunauer-Emmett-Teller), and XPS (X-ray Photoelectron Spectroscopy) to elucidate its nature and performance. The transesterification process was systematically optimized by varying parameters such as temperature, time, methanol-to-oil ratio, and catalyst loading. The optimized yield of 92.61% of biodiesel resulted under ideal conditions, specifically at 65°C, 150 min, 5 wt% catalyst loading, and an 18:1 M ratio. The biodiesel derived from PKS oil exhibited promising fuel properties encompassing cold flow properties, density, viscosity, cetane number, and flash point, validating its potential as a viable alternative fuel source. Furthermore, the synthesized novel catalyst demonstrated exceptional efficiency, retaining stability over five cycles without significant reduction in biodiesel yield. These findings underscore the viability of PKS biomass as a renewable and sustainable source for both catalyst synthesis and biodiesel production