Savanna soils of Nigeria are inherently low in nutrients (particularly nitrogen and phosphorus) thereby resulting in low yield of crops. To this end, field experiments were conducted at the Teaching and Research Farm of College of Agriculture Lafia in the Southern guinea savanna zone of Nigeria (08°30'N and 08°30'E, 18 m above sea level) during the rainy seasons of 2009, 2010 and 2011 to evaluate the yield and agronomic efficiency of cowpea varieties under varying phosphorus application rates. The experiment consisted of four levels of phosphorus in the form of single super phosphate (0, 30 and 60 kg P ha-1) and four varieties (DAN ILA, IAR-48, IT90K-277-1 and IT93K-452-1). The twelve treatment combinations were laid out in a randomized complete block design with three replications. The results obtained showed that number of pods per plant, pod yield per plant, seed yield per plant, number of seeds per pod, 100 seed weight and seed yield per hectare were significantly increased by the application of 30 kg P ha-1 in all the years of the experiment. Variety IT90K-277-1 consistently produced significantly, the highest values for all yield and yield characters measured. Agronomically, application of 30 kg P ha-1 was significantly more efficient than 60 kg P ha-1. Application of 30 kg P ha-1 to variety IT90K-277-1 produced significantly, the highest seed yield per hectare and is therefore recommended.