Blood transports lysine and other nutrients derived from the diet and ensures good health and greater productivity for the fish. Therefore, this study aimed to verify the hematological behavior of juvenile tambaqui Colossoma macropomum nourished with levels of 9.72, 12.84, 15.96, 19.08 and 22.20 g.Kg-1 of total lysine, corresponding, respectively, to the supplementation levels with L-lysine: 0.00, 4.00, 8.00, 12.00, 16.00 and 20.00 g.Kg-1 of L-lysine. The blood of the fish was collected in the initial and final periods by puncture of the caudal vein. The variables were validated by ANOVA and Tukey's test (p< 0.05). No differences were found for hemoglobin, hematocrit, CHCM, leukocytes of the eosinophil and monocyte types, and thrombocytes (p> 0.05). The changes observed in total leukocytes were not attributed to diets (p= 0.00). Means of CMV, HCM, lymphocytes and neutrophils, varied over the initial period, but not in regard to different lysine levels (p< 0.05). Thus, it is concluded that the varying lysine levels of the diets did not compromise the hematological parameters analyzed.