Moringa seed oil (MSO) was used as a feed additive to evaluate its potential to manipulate rumen fermentation and productive performance in lactating Ossimi ewes. Cold extracted MSO was supplemented at four different levels (1, 2, 3, and 4%) in diet using in vitro batch culture system for optimizing best supplementation level for sheep. Results of in vitro study revealed non-significant (P>0.05) effect of MSO on true dry matter degradability (TDMD) up to 3% inclusion level, however, decrease in TDMD was observed by 4% MSO supplementation as compared to control and other treatment groups. Accumulated gas production was significantly (P<0.05) increased by MSO supplementation while non-significant decrease in ammonia concentration was observed. Fermentation pattern and TDMD revealed 1% MSO as an appropriate level for supplementation, which was further evaluated by invivo trial. Fourteen lactating Ossimi ewes (about 3 years old with an average body weight of 51 ± 0.5 kg after 5 days of parturition) were randomly assigned into two experimental groups (seven each). One group was fed a basal diet without any supplementation and served as control. Other group was fed basal diet supplemented with 1% MSO on dry matter basis. Animals were fed these diets for a period of 45 days. Nutrient digestibility, milk production and composition were determined. Results revealed that supplementation of MSO significantly (P<0.05) increased milk yield and fat corrected milk. Similarly, it is also significantly (P<0.05) increased yield of milk components (protein, lactose, and SNF) as compared to the control group. However, milk composition (%) was not significantly (P>0.05) affected by treatment. Our study revealed that MSO could be used as a natural fat supplement to meet energy requirements of lactating sheep. Moreover, antioxidants and other bioactive compounds, present in MSO can effectively modulate rumen fermentation which makes it a potential alternative of chemical feed additives (especially antibiotics) to improve feed digestibility and utilization for increasing animal productivity.