The objective of the present study was to investigate the effect of genetic and non-genetic factors and to estimate genetic parameters of first lactation 305 days milk yield (FLMY305), 305 days fat yield (LFY), 305 days solid not fat yield (LSNFY), 305 days total solid yield (LTSY), 305 days fat percentage (FAT%), 305 days solid not fat percentage (SNF%) and 305 days total solid percentage (TS%) in Murrah buffaloes. The data of 315 Murrah buffaloes calved from 1993 to 2013 and sired by 47 bulls maintained in an organized farm at ICAR-National Dairy Research Institute, Karnal was analyzed to study the effect of genetic and non-genetic factors. Least squares analysis was done to estimate the effect of genetic and non-genetic factors on FLMY305, LFY, LSNFY, LTSY, FAT%, SNF% and TS%. Heritability estimates were obtained by using paternal half-sib correlation method. The heritability estimates for FLMY305, LFY, LSNFY, LTSY, FAT%, SNF% and TS% traits were found to be 0.30, 0.29, 0.30, 0.30, 0.05, 0.02 and 0.06, respectively. Very high and positive genetic and phenotypic correlations of FLMY305 with milk constituents’ yield traits implied that selection based on FLMY305 would result in correlated response in milk constituents yield traits and therefore need not to be considered separately for their improvement.