Abstract: The aim of this study was to examine the effects of planting density and inter-row spacing on cowpea (Vigna unguiculata L. Walp.) productivity at two contrasting moisture regimes. A field experiment was conducted under controlled moisture conditions during the 2007 off-season, at Hawassa University, College of Agriculture, Southern Ethiopia. Treatments were made from a factorial combination of four densities (71428, 95238, 133333 and 200000 plants ha-1), two inter-row spacings (50 and 70 cm) and two levels of water regimes (well watered and dry). The experiment was laid out in a split- split plot design and had three replications with watering regime, inter-row spacing and planting density as main plot, sub-plot and sub-sub-plot factors, respectively. Grain yield and all yield attributes, total biomass and harvest index were decreased by water limitation while none of those traits were significantly affected by inter-row spacing. Moisture x planting density interaction was significant for grain yield ha-1, number of pods m-2 and total biomass ha-1. The interaction indicated that an increase in both grain and total biomass yield ha-1 was observed with increasing planting density under the wet regime. Grain yield plateau was reached at a density of 160000 plants ha-1 under the wet regime. On the other hand, an increase in planting density decreased grain yield and total biomass ha-1 under the water-limited condition with the highest yield at the lowest density of 71428 plants ha-1. Thus, farmers could get more out of cowpea by matching their planting density with available moisture. The two inter-row spacings can be used interchangeably by choosing whichever is convenient for management.