The objective of this experiment was to investigate the effects of Indian odd fruit oil (IO) and combination with Yucca schidigera (YS) or rubber seed oil (RO) on in vitro rumen fermentation parameters. The treatments were as follows: 5 doses (0, 1, 2, 3 and 4% DM) of IO, 5 doses (0, 0.5, 1, 1.5 and 2% DM of IO mixed with YS (12.5 mg) (IO+YS), respectively, and 5 doses (0, 0.5, 1, 1.5 and 2% DM) of both IO and RO (IO+RO)(4 replicates per treatment). All treatments were evaluated in vitro 24 h batch culture of 25 mL rumen fluid with 0.5 g TMR (48% forage and 52% concentrate) and 50 mL basal medium. The cumulative gas production (GP) was continuously measured in an automated trace gas recording system (AGRS-III, Beijing). After 24 h, pH was determined, and samples were collected to analyze ammonia N (NH₃-N), in vitro dry matter degradability (IVDMD), neutral detergent fiber degradation rate (DNDF), acid detergent fiber degradation rate (DADF) and volatile fatty acids (VFA). Results showed that 3% and 4% DM of IO reduced the DNDF and DADF (P < 0.05), without effecting pH, NH₃-N, IVDMD, GP, total and individual VFAs, 2% DM of IO increased the concentration of acetate and propionate (P < 0.05). 4% DM of IO+12.5 mg YS supplement reduced the DNDF and DADF (P < 0.05), and did not affect pH, IVDMD, GP, the concentration of NH₃-N or total and individual VFAs. Supplementation of IO+RO increased pH (P < 0.05), while did not affect IVDMD, GP, the concentration of NH₃-N or total and individual VFAs. However, 0.5% of IO+RO increased DNDF and DADF (P < 0.05), 1% of IO+RO decreased DADF (P < 0.05). It was concluded that supplements of IO, IO+YS and IO+RO nearly had no effect on rumen fermentation.