Optimization of acid value in biodiesel production from high viscous rubber seed oil (RSO) using solid waste eggshells has been studied. A gradual reduction in acid value from 67.6 (mg KOH/ g oil) to 0.26 (mg KOH/ g oil) was observed in the synthesized biodiesel at the optimum process conditions of 12:1 methanol: oil molar ratio, 4 (wt %) catalyst concentration and 3hours of reaction time. Process parameter optimization was performed using a well organized optimization tool namely response surface methodology (RSM). It is also observed that molar ratio (mol/mol) and reaction time (h) are the more significant process parameters on the final product. Coefficient of determination R-2 value of 0.9335 observed from RSM analysis, signifies a minimum error between experimental and predicted responses.