The experiments were conducted to estimate the combining ability and heterosis in yield and yield components of cowpea (Vigna unguiculata (L.) Walp. The experiment was conducted at the Teaching and Research farm of the Department of Crop Production and Horticulture, Modibbo Adama University of Technology, Yola (Latitude 90 141 N and longitude 120 321 E) Adamawa state and at Taraba state Agricultural Development progroamme farm, Wukari (latitude 70 511 N and longitude 90 471 E) Taraba state of Nigeria. The genetic materials consisted of three local cultivars (40 days red eyes, silver beans, and iron beans) and three improved varieties (SAMPEA 15, SAMPEA 12 and SAMPEA 11) collected from the Gene Bank of International Institute of Tropical Agriculture, Kano state Nigeria. The six genotypes with genetically diverse traits were hybridized in a half diallel fashion. The six parents and 15 F1s were laid in a randomized complete block design with three replications during 2018 cropping season. Six plants were selected from the net plot for recorded observation. Data were collected for the following traits; Emergence percentage, days to 50 percent flowering, days to pod formation, days to maturity, number of pods per plant, pod weight per plant, number of seeds per pod, 100 seed weight, seed yield per plant and seed yield per hectare. Result of the analysis of variance revealed that GCA variances were highly significant for six traits, while SCA variances were highly significant for all traits. The significance of both GCA and SCA variance for most of traits indicated that both additive as well as non-additive types of gene actions were involved in the inheritance of these traits. The traits, which had higher mean squares of SCA than GCA indicated preponderance of non-additive genetic variance for those traits. The ratio of GCA/SCA (estimates of variance) is less than unity for six traits indicated the preponderance of dominance type of gene actions for the traits under study. The magnitude of heterosis varied from cross to cross. Genetic divergence would be the factor responsible for high heterosis. Heterotic response for seed yield per plant was mainly due to high heterotic desirable effects for yield components like number of pods per plant, pods weight per plant, number of seeds per pod and 100 seed weight.

Keywords: Combining ability; heterosis; yield; cowpea.