A methodology was developed to reduce the acid value of Simarouba glauca seed oil with high free fatty acid in the pretreatment. The acid value of Simarouba glauca was reduced from 6.9348 to 1.01 mg KOH/g by only one step acid-catalyzed esterification with a methanol-oil ratio of 6.5:1 (v/v), 0.88 (v/v%) H2SO4, temperature of 60 degrees C, and a reaction time of 60 min, which were chosen as the optimum parameters for the acid catalyzed esterification process. From this study, it was proved that the response surface methodology finds the suitable solution for the optimum process parameters and the subsequent experiments confirmed the validity of the model.