Nitrogen fertilization provides a great response in pasture productivity and quality but, after applied to the soil, this element undergoes several transformations, what increase its losses. To minimize this problem, a promising alternative currently suggested is diazotrophic bacteria use, which can contribute to a greater use of nitrogen by plants. This study aimed to evaluate the effect of nitrogen doses with and without inoculation of seeds with Azospirillum brasilense on the structural characteristics, chemical composition, and mass production of Urochloa decumbens cv. Basilisk. The experimental design was completely randomized, arranged in a 2 × 5 factorial scheme, with four replications. Treatments consisted of forage seed inoculation or not with Azospirillum and five nitrogen doses (0, 50, 100, 150, and 200 kg ha-1). The variables analyzed were plant height, number of tillers, shoot dry mass (SDM), root dry mass (RDM), SDM/RDM ratio, chlorophyll index, nutrient content in forage shoot, crude protein (CP), neutral detergent fiber (NDF), and nitrogen use efficiency. The inoculation of forage seeds with A. brasilense associated with nitrogen doses up to 100 kg ha-1 contributed positively to dry mass, plant-shoot nutrient content and bromatological composition of U. decumbens cv. Basilisk. The inoculation of seeds of U. decumbens cv. Basilisk, with A. brasiliense, is a viable alternative for partial substitution of nitrogen fertilization.