Combining ability variances and their effects were studied for six important characters in Line X Tester mating design comprising of 36 crosses from 4 lines and 9 testers in cowpea. Analysis of variance revealed considerable amount of variability among the parents and hybrids for all the traits studied The magnitude of specific combining ability variance was higher than general combining ability variance for all the traits indicating the predominance of non-additive gene action APC-714 and APC-761 were good general combiners for water use efficiency (WUE) among the testers. KBC-1 and KBC-2 were the good general combiners for net assimilation rate (NAR), leaf area duration (LAD) and WUE. respectively, among the lines. TVX-944 x APC-714 was identified as potential cross for exploitation in the breeding program for WUE and its components.