This paper explores the feasibility of converting waste Rohu fish (Labeo rohita) scale into a high-perfor-mance, reusable, low-cost heterogeneous catalyst for synthesis of biodiesel from soybean oil. Thethermo-gravimetric analysis (TGA) and X-ray diffraction (XRD) analysis revealed that a significant por-tion of the main component of fish scale i.e. HAP (hydroxyapatite) could be transformed into b-tri-cal-cium phosphate when calcined above 900 ?C for 2 h. Scanning Electron Microscopy (SEM) morphologystudies of the calcined scale depicted a fibrous layer of porous structure; while a BET surface area of39 m2/g was measured. Response surface methodology (RSM) was employed to determine the optimalparametric conditions viz. methanol/oil molar ratio, 6.27:1, calcination temperature, 997.42 ?C and cat-alyst concentration, 1.01 wt.% of oil corresponding to a maximum FAME yield of 97.73%. Reusabilityresults confirmed that the prepared catalyst could be reemployed up to six times, procreating a poten-tially applicable avenue in biodiesel synthesis.