To evaluate biomass components of Massai grass under five doses of N (0, 150, 300, 450 and 600 mg N/dm³ soil) during three cycles of growth (establishment, regrowth 1 and regrowth 2) this study was carried out. The experiment was carried out in a greenhouse, in a completely randomized design with measures repeted over time and five replications. In the three cycles, nitrogen doses had increasing linear effect on green herbage dry matter (GHDM), green leaf dry matter (GLDM), on the tiller population density (TPD) and on forage density. Canopy height and foliage height were the highest ones in establishment of regrowth 2, respectively, and they decreased at the highest doses of nitrogen. Irrigation depth was the greatest at the highest doses and in regrowth 1. Water use efficiency responded positively to the doses, being the regrowth 2 the highest values were obtained at the highest doses of nitrogen. Nitrogen use efficiency by Massai grass is influenced by fertilizantion as well as by the cycles. Nitrogen fertilization has positive effects on the components of Massai grass biomass.