The purpose of this study was to evaluate the effects of coating whole cottonseed (WCS) with varying quantities of starch on in vitro ruminal fermentation. In vitro fermentation experiments were conducted over two days, with three replicates per day (n = 6). Each trial consisted of three treatments (control, 1% starch, and 5% starch). The control was an uncoated WCS, the 1% starch treatment consisted of WCS coated with 1% starch, and the 5% starch treatment was WCS coated with 5% starch. For the 5% starch treatment, the pH of the rumen fluid was lowest, total gas production was highest during the initial stage, NH₃-N content was 25% lower than that of the control (P<0.05%), the acetate ratio at 48 h was reduced by 7.0%, and the propionate ratio increased 7.5% compared to that of the control (P<0.05). For the 1% starch treatment, the pH was not different from that of the other treatments except at 3 h after the start of incubation, and total gas production and NH₃-N content were not different from those of the control. Consequently, coating WCS with 5% starch altered the in vitro ruminal fermentation parameters; however, 1% starch treatment did not alter ruminal pH, total gas production, NH₃-N, or VFA composition, relative to the control.