Biodiesel, an eco-friendly and sustainable alternative to diesel, has gained increasing interest over the past few years. The reuse of waste cooking oil as a feedstock for biodiesel production is affordable and environmentally safe. This study aimed to understand the understudied benefits of using zinc-doped biochar as a catalyst for biodiesel production. The zinc-doped biochar catalyst was characterized using techniques such as scanning electron microscope with energy-dispersive X-ray (SEM-EDAX) analysis and Fourier transform infrared (FTIR) analysis, which revealed the morphological and functional characteristics of the catalyst. The optimum process conditions were found to be catalyst concentration of 3.92% (w/w), methanol-to-oil molar ratio of 16:1, reaction temperature of 65 degrees C, and reaction duration of 66.5 min; these conditions yielded 94.1% biodiesel using a response surface optimization technique. The produced biodiesel was analyzed using gas chromatography-mass spectrometry, and the presence of methyl esters was confirmed. The use of waste cooking oil and biochar catalyst for biodiesel production is an economical and environmentally sustainable process.