This study evaluated the effectiveness of mannan oligosaccharides (MO) supplementation in fish meal (FM), soybean meal (SBM) and soy protein concentrate (SPC) formulated feeds for snakehead, Channa striata (Bloch 1793) in a two-way factorial experiment. Factors were diet (FM, 40% FM replacement by SBM, and 40% FM replacement by SPC) and MO supplementation (0%, 0.2%, or 0.4% MO). Growth was significantly affected (p0.05). Red blood cell counts were not significantly affected (p>0.05) by diet, MO supplementation, or the interaction, but white blood cell counts were significantly affected (p0.05). Following a 15-d bacterial challenge with Aeromonas hydrophila, lysozyme levels were significantly increased (p0.05). Our results suggest that MO supplementation may improve diet performance in snakehead culture, although full-scale commercial trials should be conducted to confirm this.