The purpose of this study was to identify parents and obtain segregating populations of cowpea (Vigna unguiculata L. Walp.) with the potential for tolerance to water deficit. A full diallel was performed with six cowpea genotypes, and two experiments were conducted in Teresina, PI, Brazil in 2011 to evaluate 30 F2 populations and their parents, one under water deficit and the other under full irrigation. A triple-lattice experimental design was used, with six 2-m-long rows in each plot. Sixteen plants were sampled per plot.