Lactic acid is a product that finds several applications in food, cosmetic, pharmaceutical and chemical industries. The main objective of this work is to evaluate potential use of the sap from palmyra (Borassus flabellifer Linn.) and oil palm (Elaeis guineensis) as substrate for lactic acid production by Lactobacillus casei TISTR 1500. The effects of acid hydrolysis, pH control and nutrient supplement of palmyra sap and oil palm sap on fermentation performance were investigated. It was found that lactic acid fermentation using palmyra sap was not significantly affected by either acid hydrolysis or pH control. The addition of MRS increased biomass and product yield. The final lactic acid concentration, dry cell weight and productivity were increased by increasing the total sugars of palmyra sap concentrations up to 134.0 g L^-1. The kinetic parameters for the palmyra sap at 134.0 g L^-1 total sugars were calculated to be of: specific growth rate (µ) 0.05 h^-1, the maximum productivity (R_M) 2.02 g lactic acid L^-1 h^-1, cellular yield coefficient (Y_X/S) 0.20 g cell g^-1 sugar, and lactic acid yield (Y_P/S) 0.78 g g^-1. When oil palm sap was used as carbon source for L. casei TISTR 1500, pH control did not significantly affect lactic acid production. The addition of MRS medium into oil palm sap improved the biomass and the product yield for which the lactic acid production in static flask at 37ºC and pH 5.5 using 20 g L^-1 of total sugars was improved to be of 0.55 g L^-1 h^-1. Oil palm sap could be served as a good potential source of raw materials for efficient production of lactic acid by L. casei TISTR 1500.