This work was carried out at Sakha Agricultural Research Station, during the summer seasons of 2004 and 2005 on cowpea. The main objective of this research was to evaluate three cultivars (Kaha-1, Kafr El-Sheikh-1 and Dokki-331) and new superior line (A₇) of cowpea under three nitrogen fertilizer levels (15, 30 and 45 kg N fed.^-1) and two plant populations (60.000 and 120.000 plant fed.^-1). A split-split plot in a randomized complete blocks design with four replicates was used. Results are summarized as follow: Dokki-331 cv. surpassed the other genotypes in plant height, number of leaves plant^-1, number of branches plant^-1 and leaf area plant^-1. However Kaha-1 cv. produced the lowest values of vegetative traits in both seasons. The Kafr El-Sheikh-1 cv. surpassed in number of peduncle of pods plant^-1 in both seasons. Moreover, seed yield and its components, i.e., seed yield fed^.-1, number of pods plant^-1, number of seeds per pod and weight of 100-seeds, the lien A₇ surpassed the other genotypes followed by Kafr El-Sheikh-1 cv. However, Dokki-331 cv. produced the lowest seed yield and yield components in both seasons. In addition, the lien A₇ surpassed in leaf's chlorophyll and seed's protein content. Less plant density improved vegetative growth characters, as well as yield components and increased leaf contents of chlorophyll and seed content of protein. While, seed yield were increased as a sequence of increasing plant population in both seasons. The results indicated that increasing applied N rate up to 45 kg N fed.^-1 was accompanied with significant increases in vegetative growth characters, meanwhile, increased number of peduncle of pods plant^-1 with the application of 30 kg N feddan^-1. Moreover, seed yield and its components were increased as a sequence of increasing N level up to 45 kg N fed.^-1, also, leaf's chlorophyll and seed's protein content positively and significantly reflected.