The mating of closely related animals has long been known to lead to ‘inbreeding depression’ as a result of loss of fitness. On the other hand, crossbreeding animals leads to increased hybrid vigour since the offspring generally speaking, perform better than the average of the parental breeds. Thus, crossbreeding is an important animal breeding tool for the improvement of traits like growth, musculature and survival. Preweaning traits of sheep which influence flock productivity include birth weight, weaning weight, average daily gain to weaning and weaning rate. These traits are in turn influenced by genetic and environmental factors. The objective of this study was to assess the effects of crossbreeding, season, sex and type of birth on the growth performance of crossbred Yankasa, Balami and West African Dwarf lambs sired by 14 sires mated to 147 ewes. Results indicated that single born lambs were significantly heavier (P