This study evaluated the growth performance, hematological and biochemical profiles of paiche fed diets with 36, 40, 44, 48 and 52% crude protein content (CP) and a constant energy to protein ratio (37.7 kJ g-1). One hundred and fifty pirarucu (68.75 ± 3.11 g) were randomly divided into 15 tanks and fed for 75 days. Weight gain (WG), feed conversion ratio (FCR), specific growth rate (SGR), daily feed intake (DFI), daily protein intake (DPI), protein efficiency ratio (PER), hepatosomatic index (HSI), visceral somatic index (VSI), chemical composition of fillet and liver and feed apparent digestibility coefficient (ADC) were evaluated. Fish blood samples were analyzed for hemoglobin [Hb], hematocrit (Ht), red blood cells, white blood cells, thrombocytes, corpuscular index, glucose (GLY), total plasma protein (TPP), cholesterol (CHOL) and triglycerides (TRY). Feed protein and energy ADCs were the highest at 36, 40 and 44% CP and 40, 44 and 48% CP, respectively. Best FCR, WG and SGR were observed for fish fed 44 and 48% CP. In turn, fish fed 48 and 52% CP had the highest HSI, VSI and liver lipids. Fish fed 36 and 40% CP presented the highest DFI, while DPI was lower in fish fed 44%. The highest PER values occurred at 44 and 48% CP. Dietary protein levels had no influence on tissue protein and lipid concentrations. The highest values of Ht and Hb, CHOL, TPP and TRY were observed at 48 and 52% CP. Best performance and health of pirarucu juveniles were achieved with 45.8% CP.