The extract of rambutan (Nephelium lappaceum L.) peel had been studied for its bioactive compounds that could inhibit the production of alcohol in fermentation. This research focused on the application of rambutan peel extracts to control cassava tapai fermentation. Extracts were prepared through maceration with two solvents of different polarities, which were ethanol (polar) and ethyl acetate (semi-polar). The rambutan peel extracts were applied in the cassava tapai in different concentrations (0.5, 1.0 and 1.5% w/v, db). Three methods of packaging were employed to prepare the cassava tapai included plastic bag with small holes, banana leaf and banana leaf inside bamboo box. Fermentation was held for 6 d and the physicochemical properties of cassava tapai were analyzed each day. These included alcohol content, total reducing sugar, total titratable acidity, pH and total yeast and mold count. The results indicated that the addition of both ethanolic or ethyl acetate rambutan peel extract showed inhibition of alcohol production in cassava tapai prepared with plastic, banana leaf and bamboo box packaging. For example, at day 6, the alcohol content of cassava tapai prepared with banana leaf with no extract addition was 4.97±0.29%, and those added with 1.5% ethanolic extract was 3.94±0.44%. The alcohol content of cassava tapai added with 1.5% ethyl acetate extract and prepared with plastic packaging was 3.63±1.00% at day 6. This was significantly lower than the alcohol content of the control, which was 6.70±0.96%. The results demonstrated that rambutan peel extracts obtained either with ethanol or ethyl acetate extraction exhibited the existence of fermentation inhibitor compound(s) that controlled/lowered the alcohol content in cassava tapai fermentation.