The rambutan (Nephelium lappaceum L.) fruit peels and its ethanolic extract have been reported to have activity to inhibit cider and tapai fermentation. This research was aimed to investigate the rambutan peels and extract as a potential fermentation inhibitor to delay spontaneous alcohol fermentation in palm sap in alcohol production. Fresh rambutan peels and rambutan-peel ethanolic extract were applied to palm sap in three different concentrations. Physicochemical properties of palm sap (pH, total dissolved solids, total reducing sugar, total titritable acidity, and alcohol content) were observed during 7-d fermentation. The addition of 35% and 45% fresh rambutan peels could delay alcohol fermentation in palm sap until 3-d fermentation, while 40% fresh rambutan peels could prevent alcohol production until 4 days of fermentation. The addition of 35, 40, and 45% rambutan peels in palm sap produced 7.39±0.15%, 6.26±0.08%, and 5.30±0.15% as the highest alcohol contents, respectively comparable to alcohol content of palm sap control which was 7.19±0.50%. The addition of 1.5% ethanolic extract could also delay the alcohol fermentation palm sap until 2-d fermentation, while 3.0, and 4.5% ethanolic extract could delay alcohol formation until 3-d fermentation. The addition of 1.5, 3.0, and 4.5% ethanolic extracts palm sap produced 6.13±0.09%, 4.17±0.09%, and 6.06±0.12% as the highest alcohol contents, respectively comparable to the alcohol content of palm sap control which was 6.43±0.11%. Subsequently, palm sap with the addition of fresh rambutan peels and ethanol extracts were distilled at 78-80 oC for 5 hours. The addition of 45% fresh rambutan peels and 1.5% ethanolic extracts produced the highest yield of distillate and yield of alcohol with 35.20±1.11% and 27.57±0.14 alcohol contents, respectively.