The aim of the current study was to investigate the environmental factors potential sources of variation for postweaning traits in Buchi sheep maintained at the Livestock Experiment Station Jugaitpir, Pakistan. Data were collected from 1986 through 2010. Means ± SE were 16.58 ± 0.04 kg for weight adjusted to 180 days of age, 22.62 ± 0.05 kg for weight adjusted to 270 days of age and 33.78 ± 0.067 kg for weight adjusted to 365 days of age. Statistical analyses were performed by using the mixed procedure of the SAS statistical package. The model included the effects of year and season of birth, sex, type of birth, parity, age and weight of dam at lambing, and two-way interactions between these factors. Results showed that all postweaning traits were significantly (P < 0.05) affected by year, interaction between year and season, and interaction between year and sex of lamb. A significant interaction (P < 0.05) between season and sex existed for the weights adjusted to 180 and 365 days of age. These two traits were also affected (P < 0.05) by sex of lamb. Season, type of birth, parity, age and weight of dam were not important sources of variation for postweaning traits in this population. These results suggested that the feeding and management would need to be flexible to face any harsh climate and feed scarcity situation to maintain a productive and profitable sheep production system with Buchi sheep.