The present investigation was carried on crossbred cattle maintained at Instructional Dairy Farm, Nagla of G.B. Pant University of Agriculture and Technology, Pantnagar. The study was conducted on 700 crossbred cattle, the progeny of 68 sires distributed over 28 years from 1990-2017. The first lactation monthly milk yield (FLMMY) data were utilized, which were collected from history sheets of crossbred cattle. A total of 10 FLMTDY were taken from each animal. The data were subjected to LSMLMW and MIXMDL package of Harvey (1990) to estimate the least-square mean, the effect of genetic and non-genetic factors on trait under study, genetic and phenotypic parameters of part milk yields. The least-squares mean of monthly test-day milk yields (MTDMY) starting with 8.50 kg (MTDMY-1) showed the peak yield at MTDMY-2 (10.55 kg) and lowest for MTDMY-10 (8.07 kg). The heritability estimated for the first lactation monthly milk yield (FLMMY) was low to medium. The genetic and phenotypic correlations between FL305DMY with FLFMY and FLMMY were found positive. Our results indicated that the selection might be made based on part lactation yield at an early stage.