At inadequate stocking density, fish generally show different physiological responses. The effects of stocking density on Arapaima gigas larvae productive parameters have been determined in a previous study. This study aimed to evaluate the effect of the stocking density on the water quality, hematological and biochemical profile, and productive performance of juvenile A. gigas. One hundred and eighty twelve months old, A. gigas were distributed into tanks using initial densities of 103.90, 157.95 and 220.11 kg m-3 with three replicates. Ammoniacal nitrogen, carbon dioxide, dissolved oxygen pH, alkalinity, and hardness were determined using a LaMotte Fish Farm 9, AQ-2 model, Maryland, USA, freshwater test kit. Blood samples were taken at 13, 14, and 15 months old by pricking the caudal vein and profiles of glucose (Glu), total protein (TP), albumin, aspartate transaminase (AST), alanine transaminase (ALT), and urea, were determined in blood serum. Rearing water was saturated in ammoniac nitrogen, carbon dioxide, and dissolved oxygen but have not changed with the increase of stocking density (P < 0.05), Erythrocyte's count (EC) diminished (P < 0.05), nonetheless, hemoglobin, mean concentration hemoglobin (MCH) and mean cell volume (MCV) increased (P < 0.05). Albumin, AST, ALT and urea diminished at 220.11 kg m-3 stocking density (P < 0.05). The feed intake increased, final biomass gain was 100.26 ± 19.00, 119.10 ± 13.95, and 130.24 ± 08.07 kg m-3, but did not change as density increased (P < 0.05). Juveniles of A. gigas showed no variation in productive performance with an increase in the stocking density. Furthermore, hematological and biochemical adapting profile to high stocking densities characterized this species.