Analyzing digestive enzyme concentration in the gut is important to know about the digestive physiology of fish. Therefore, we determined concentrations of protease, lipase, and amylase enzyme in gut extracts of juvenile and adult groups of Notopterus notopterus relative to total body length (TBL), body weight (W), gut length (GL), relative gut length (RGL), Zihler's index (ZI) and condition factor (K). A total of 60 N. notopterus specimens (30 juvenile and 30 adult) were collected, the gut of each removed, homogenized, and evaluated for the concentrations of protease, lipase, and amylase. Protease and lipase concentration were observed significantly (P < 0.01) correlated with increased TBL, W, and GL in both juvenile and adult groups of N. notopterus. Amylase concentration significantly (P < 0.01) increases with an increase in TBL, weight, and GL in the juvenile group, whereas amylase concentration significantly (P < 0.01) decreases with an increase in TBL, W, and GL in the adult group. K had a significant (P < 0.01) positive correlation with protease and lipase concentrations in both juvenile and adult groups, whereas K showed a significant (P < 0.01) positive correlation with amylase concentrations in juvenile and significant (P < 0.01) negative correlation in the adult group. Protease and lipase concentration were observed significantly (P < 0.01) correlated with an increase in ZI in the juvenile and adult groups. Amylase concentration significantly (P < 0.01) increases with an increase in ZI in the juvenile group, whereas amylase concentration significantly (P < 0.01) decreases with an increase in ZI in the adult group. The concentrations of protease (344.12 U/mg) and lipase (172.49 U/mg) were observed high in juvenile and adult groups, whereas amylase concentration (3.80 U/mg) was found low in the juvenile and adult N. notopterus groups. Present study results revealed the digestive physiology and carnivorous behavior of N. notopterus. Moreover, information from the present study about digestive enzyme concentration in juvenile and adult species of N. notopterus provides valuable information to understand the digestive physiology of carnivorous fishes.