The objective of this study was to evaluate the use of virginiamycin (VM) and the supplementation level on the performance of Nellore cattle in their post-weaning phase grazing on Brachiaria brizantha ‘Marandu’ during the wet season. We hypothesized that VM works on the gram-positive bacteria by inhibiting processes that result in loss of energy, modulating the ruminal fermentation and promoting an improvement in animal performance. The following supplements were utilized in this experiment: mineral (ad libitum) and protein (0.1% of BW), with or without inclusion of VM. The experiment was conducted from January to March 2014, divided into 3 25-d periods. Eighty (80) post-weaning uncastrated Nellore, with an average initial BW of 205.4 ± 21.9 were used in the experiment. Animals were weighed at the end of each period, after a solid food-deprivation period of 16 h. Data were analyzed in randomized blocks with repeated measures over time, in 2 × 2 factorial arrangement in which the factors were the supplements and lack or inclusion of VM. The paddock was considered the experimental unit, with 4 paddocks per treatment (5 animals/paddock). Means were compared by the t-test at 10% probability, and a trend at 15%. There was no interaction between VM and the supplementation level (P = 0.78). It was considered that there was an upward trend of 0.06 kg in ADG for animals fed VM (P = 0.16), which resulted in the increased final BW of the animals fed VM (269.5 vs 264.8; P = 0.09). The protein supplement provided an additional gain of 0.09 kg/day as compared with the mineral supplement, which represented a 11% higher ADG (P = 0.03) and an increase in BW (271.7 vs 262.6; P = 0.01). The highest ADG (P < 0.01) was observed in the first period (1.01 kg), decreasing by 48% in the second period, and increasing by 0.30 kg/day in the third period as compared with the second; this variation was due to the climatic conditions. The use of VM and protein supplement improves animal performance during the wet season. Acknowledgments: Paraíso Nutrição Animal.