This research was conducted during the two summer seasons of 2009 and 2010 at South Tahrir, Experimental Farm of Horticulture Research Institute, AgricultureResearchCenter (A R C), Beheira, Governorate, Egypt. This study carried out to evaluate the possibility of using different rates of biofertilizer instead a part of chemical fertilizers for optimal nutrition and some attributes of cowpea. The chemical fertilizers were as four levels of recommended fertilization doses of N, P and K fertilizers i.e. 0, 50, 75 and 100 %/ fed. Five treatments of microbial inoculations (biofertilizer) i.e.without microbial inoculation (B0), inoculations with Azospirillum sp. and Trichoderma sp. for nitrogen (B1), Bacillus megaterium for phosphorus (B2), Pseudomonas fluorescensfor potassium (B3) and the mixtures of all previous of microbial inoculations (B4).         The obtained results indicated that there were gradually significant increases due to fertilize cowpea plants with 75 % from the recommended fertilization on various obtained characters. Also,treating seeds of cowpea with the mixtures of all microbial inoculations of Azospirillum sp. and Trichoderma sp., as well as Bacillus megaterium and Pseudomonas fluorescens markedly enhanced effect on cowpea growth, total dry seed yield (ton/ fed.) and pod characters, nitrogen (%), phosphorus (%), potassium (%) content in leaves as well as protein (%) content in seeds.         The interactions between application of the 75 % recommended fertilization and treating cowpea seeds by mixtures of all microbial inoculations helped in producing the most pronounced effects of all vegetative growth characters, total dry seed yield (ton/ fed.), pod characters, nitrogen, phosphorus, potassium content (%) in leaves and protein content (%) in seeds. Seed inoculations with individual Azospirillum sp. and Trichoderma sp. obtained the superiority treatment for vegetative growth characters and nitrogen (%) in leaves and protein content (%) in seeds. Seed inoculations with individual Bacillus megaterium and individual Pseudomonas fluorescens obtained the most effective treatment for total dry seed yield (ton/ fed.), pod characters, phosphorus (%) and potassium content (%) in leaves, respectively when compared to the control untreated plants.