An 80-day feeding trial was conducted in a recirculation system aquarium operating at 26 ± 0.3 °C, to evaluate the nutritive value of Vicia peregrina seed as a possible protein source in the diet of mirror carp (Cyprinus carpio) fingerlings. Vicia peregrina seed was included in the diets at different levels, viz. 100, 200, 300 g heat-treated and 100, 200, 300 g raw seed in experimental diets designated A1, B1, C1, A2, B2 and C2, respectively. Growth parameters of the fish fed these diets were compared to fish receiving a fish meal and soyabean meal based control diet. On the basis of the specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER), the control and diets A1, B1, C1 and A2 were similar and significantly better than diets B2 and C2. Fish fed diets B2 and C2 showed a lower growth performance compared to those fed diets A1, B1, C1 and A2. Whole body fat content of the fish fed the diets containing the higher levels (>10%) of raw V. peregrina was significantly lower than in fish in the other treatments. Vicia peregrine seed has a potential as an alternative feed ingredient. It can be used without any adverse effects at up to 10% of the diet as a protein source in diets for fingerling mirror carp. However, the seed should be heat-treated if inclusion rates are to exceed 10% of the diet. Keywords: Culban, Vicia peregrina, nutritive value, heat treatment, mirror carp, growth South African Journal of Animal Science Vol. 36 (4) 2006: pp. 235-24