Rambutan (Nephelium lappaceum L.) peel extracts have been reported to contain potential fermentation inhibitor(s) that retard the development of alcohol in cider as the model system. This research was aimed to investigate the stability of the extracts which may contain fermentation inhibitor component(s) against heat treatment and to determine its identity. Rambutan peels were extracted using two different solvents, which were ethanol (polar) and ethyl acetate (semi-polar), by the maceration method. The extracts were subjected to heat treatments at room temperature, 60, 80, and 100 °C and applied (1.5% w/v) to cider, which were then fermented for 21 days. Physicochemical properties of the cider, such as total titratable acidity, total reducing sugar, total dissolved solid, pH, and alcohol content were observed every three days. The application of heat-treated ethanolic and ethyl acetate extracts of rambutan peel inhibited the formation of alcohol in cider, resulting in values of 1.41±0.39% and 0.56±0.32% at the highest, respectively, at the end of the fermentation period of 21 days. On the other hand, ciders made without the addition of extracts for ethanolic batch and ethyl acetate batch were capable of producing 8.06±0.23% and 5.78±0.98% of alcohol, respectively. LC-MS results indicated that several components with m/z ratio of approximately 118.0857, 190.1070, 291.0865, 303.0131, 455.3522, and 579.1516 Da, predicted to be valine, castanospermine, catechin or quercetin, ellagic acid, triterpenoid, and procyanidin B-2, respectively, were responsible as the fermentation inhibitor components of rambutan peel extract.