This study has assessed the effects of parity on lactation length, lactation milk yield, and lactation curves for each lactation stage at Haramaya University dairy research and teaching farm. Thirty-one synchronized Holstein Frisian crossbred heifers; with nearly similar age were selected and stall-fed for the whole lactation period. Data were collected on daily milk yield at each stage, days in milk and lactation milk yield, 305 days milk yield, and analyzed using the t-test for means. There was an insignificant effect on lactation length, total lactation milk yield, 305 days total milk yield, mid and late lactation milk yield between the 1 st and 2 nd lactation numbers. The rate of variation was very high (13.4%) during the early lactation stage. The daily milk yield was significantly influenced by parity (P<0.05). The variation rate of milk yield in the morning milking was ranging from 10-51%.Further study is required to examine additional aspects of parity on lactation traits such as milk composition and reproductive traits with more lactation numbers