Abstract: The study under taken investigates the effects of some non-genetic factors (Sex of calf, year and season of birth, parity and calving difficulty) affecting on birth weight in Sistani cattle. Data were collected on 932 (466 males and 466 females) Sistani calves from the progenies born in the Sistani Cattle Research station of Sistani and Baluchistan province in Iran during the period from 1989-2007. Analysis of variance indicated that the effects of sex of calf, year and season of birth, parity and calving difficulty with gestation length as a covariate on birth weight were significant (p<0.01). The least square mean for birth weight of Sistani calves was found to be 24.143±0.509 kg. The effect of calf sex on birth weight was highly significant (p<0.01). Male calves were 1.935 kg heavier at birth than females. Birth weights of male calves were 7-8% heavier than female calves. The winter born calves had the highest (25.168 kg) birth weight. Calves born in early parities were lighter in weight than those born to late-parity dams. Difference between the means for maximum and minimum years is 6.023 kg. Sistani cattle difficult calving occurred in 1.2%. First parity cows exhibited more frequent calving difficulty whereas among other parities there were no statistically significant differences.