Abstract: Indiscriminate use of insecticides is a major concern due to its ubiquitous occurrence and potential toxicity to aquatic animals. This study investigated the adverse effects of lambda-cyhalothrin (LCT; C23H19ClF3NO3) andmethomyl (MTM; C5H10N2O2S) on immune systemmodulations and growth performance of juvenile fishes. The supportive role of a taurine (TUR; C2H7NO3S)-supplemented diet was also evaluated. Juvenile O. niloticus fishes were exposed to LCT (0.079 g/L),MTM(20.39 g/L), or both in water and were fed on a basal diet only or taurine-supplemented basal diet. Exposure to LCT and MTMretarded growth and increasedmortality rate. LCT andMTMreduced antioxidant enzyme activities (superoxide dismutase and glutathione peroxidase) and innate and humoral immunity but upregulated interleukin and chemokine expressions. Moreover, exposure to LCT andMTMelevated 8-OHdG levels and increased themortality of Oreochromis niloticus after the experimental bacterial challenge. The TURenriched diet enhanced antioxidant enzymes and acted as a growth promoter and anti-inflammatory agent. TUR canmodify innate and adaptive immune responses. Furthermore, TUR supplementation is a beneficial additive candidate formitigating LCT andMTMtoxicitiesmixed with O. niloticus aquafeed.