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Chicken gut meal (CGM) is reasonably priced and rich in nutrients and can become a new source of protein in the diets of major aquatic products, such as fish and shrimp. An 8‐week feeding trial was conducted to comprehensively investigate the beneficial effects of CGM on juvenile Fat Greenling Hexagrammos otakii. Juveniles (1.58 ± 0.06 g [mean ± SE]) were fed with different levels of CGM in replacement of fish meal (FM) in the basal diet: 0% (CGM0), 25% (CGM25), 50% (CGM50), 75% (CGM75), and 100% (CGM100) replacement, representing a dietary CGM level of up to 40 g/kg. The results showed that the percent weight gain; specific growth rate; feeding rate; feed conversion ratio; hepatosomatic index; and apparent digestibility coefficients of dry matter, protein, and lipid were significantly improved among the experimental groups. Moreover, the activities of superoxide dismutase and catalase were significantly increased in the CGM25 and CGM50 groups, respectively. The activities of acid phosphatase and alkaline phosphatase were significantly decreased in the CGM75 and CGM100 groups. Triglycerides and total cholesterol were significantly increased in the CGM50 and CGM75 groups, respectively. Fish in the CGM100 and CGM75 groups had significantly higher activities of aspartate aminotransferase and alanine aminotransferase than the control. Moreover, the relative expression levels of the fatty acid synthase and acetyl‐coenzyme A carboxylase alpha genes were significantly increased in the CGM75 and CGM100 groups, while the gene expression levels of hormone‐sensitive lipase and peroxisome proliferator‐activated receptor alpha were significantly decreased. In summary, the optimal replacement level of FM with CGM was shown by curve equation analysis to be 61.30%, and their dosages were 24.52 and 15.48 g/kg, respectively. Impact statementChicken gut meal, a major terrestrial animal protein source that is rich in high levels of proteins and lipids, can be used as a good substitute for fish meal in fish diets. The price of chicken gut meal is much lower than fish meal, reducing costs. Also, the reduction of fish meal use can restore the diversity and stability of marine fish stocks. Therefore, the use of chicken meal is important for people's health and well‐being as well as the sustainable development of marine fisheries. Chicken gut meal, a major terrestrial animal protein source that is rich in high levels of proteins and lipids, can be used as a good substitute for fish meal in fish diets. The price of chicken gut meal is much lower than fish meal, reducing costs. Also, the reduction of fish meal use can restore the diversity and stability of marine fish stocks. Therefore, the use of chicken meal is important for people's health and well‐being as well as the sustainable development of marine fisheries.