An 8-week feeding trial was carried out to test Moringa oleifera leaf meal (MOLM) as a replacer for mustard oil cake in feeds for juvenile- Labeo rohita (initial mass 5.27 ± 0.01 g). Solid-state fermentation of MOLM was performed using Aspergillus niger and termed FMOLM. Five isonitrogenous (31% crude protein) and isocaloric (350 kcal/100 g) diets were prepared with different levels of MOLM by replacing mustard oil cake (MOC) viz., C (0% MOLM ), T1 (15% MOLM), T2 (30% MOLM), T3 (15% FMOLM) and T4 (30% FMOLM). One hundred and ninety-five acclimated juveniles were distributed to five experimental groups (Tank size 1000 litre) in triplicate, and they were fed daily twice up to satiation. The T4 group showed significantly (p < 0.05) higher weight gain, specific growth rate, protein efficiency ratio and lower feed conversion ratio among different treatments. Protease, amylase, aspartate aminotransferase and alanine aminotransferase were significantly (p < 0.05) higher in T4 compared to T1 and T2 groups. The incorporation of MOLM elevated oxidative enzymes such as superoxide dismutase and catalase. However, their activities were reduced in fermented MOLM groups. In conclusion, 15% MOLM can be incorporated into the diet of Labeo rohita without compromising the growth of fish. However, fermented MOLM can be utilised up to 30% level in the diet of Labeo rohita, ensuring its better growth.