There is an increasing concern about conservation and utilization of livestock local breeds. To that end, it is required to quantify the productive potential of the breeds, as well as characterizing their productive system. However, there is usually a lack of reliable data on performances for minority local breeds, which might condition on decision making. This is specially the case of the Spanish Ojinegra Sheep breed. A study was carried out to determine factors affecting live weight (LW) and body condition score (BCS) of ewes of the Ojinegra sheep breed, both at lambing and at weaning; and live weight at birth (LWb) and average daily gain (ADG) of their lambs, in commercial flocks. LW and BCS at partum (43.3 ± 7.4 kg y 2.55 ± 0.45, respectively), at weaning (42.3 ± 7.3 kg y 2.73 ± 0.45) and its variation (-0.95 ± 3.97 kg y 0.23 ± 0.36) were influenced by the age of the animal, the lambing season and the farm (p ≤ 0.05). BCS at lambing and the variation of BCS along lactation were affected by number of birth lambs (p < 0.05). LWb and ADG (3.5 ± 0.67 kg y 168 ± 51 g/day) were affected by lamb’s gender, birth rate, dam’s age at parturition, dam’s BCS at lambing and the farm (p < 0.05). ADG was also affected by lambing season, whilst LWb was affected by the interaction of factors “lambing season*lamb birth type”. The farm itself was a determinant factor, representing up to 31% of variability in some parameters. Variation among farms might be explained both by management particularities and/or genetic heterogeneity within the breed.