The present study was carried out to evaluate the effect of mustard oil supplementation during transition period on milk composition and calf birth weight of Murrah Buffaloes. The study was carried out at Livestock Research Centre, NDRI, Karnal, using 16 advanced pregnant Murrah buffaloes. Buffaloes of similar body weight and condition, parity and age were selected and randomly allotted to control and treatment group of having 8 animals each. The buffaloes under treatment group received 200 gram/head/day. Mustard oil mixed along with concentrate as per NDRI feeding ration while the control group received molasses (500gm/day/head) as per traditional NDRI ration during transition period to maintain iso-energy feeding in both the groups. Milk samples were collected on 7th, 14th, 21st day for the analysis of milk fat, protein, solid non-fat (SNF) and lactose content. Results of milk analysis revealed highly significant improvement in milk fat percentage (P<0.01) in treatment group as compared to control groups. However mean difference of protein, SNF and lactose between control and treatment group were statistically non-significant. Thus it can be concluded from the study that 200g/h/d Mustard oil supplementation during transition period improved the milk quality and calf birth weight in Murrah buffaloes.