The aim of this study is to investigate the polymorphism of the Pituitary transcription factor (PIT-1) and Prolactin (PRL) genes in Holstein Friesian cows (HF) bred in Vietnam and their effects on milk yields. For these purposes, 125 HF dairy cows of milking age from Da Lat Milk Farm located in Lam Dong, Vietnam were sampled. Phenotypic data of milk yields (calculated on 305-day of milking cycle; kg/day) of each individual milking cow were collected. The PIT-1.E2, PIT-1.E6, PRL.E3 and PRL.E4 genotypes were analyzed using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method with restriction enzymes TaqI, HinfI, RsaI, respectively. The significant effects of PIT-1.E6, PRL.E3 and PRL.E4 polymorphisms on milk yields were not observed in HF dairy cows (P > 0.05). However, results revealed statistically significant associations between PIT-1.E2 polymorphism and milk yields of HF dairy cows; individuals carrying the AA genotype yielded more milk compared to others. Our study suggests the potential use of PIT-1.E2 SNP in marker assisted selection (MAS) for improved milk yields of HF dairy cows bred in Vietnam.