Toasting causes slight reduction in the phytate content of Lima bean, thus requiring further treatment for effective utilization when incorporated into fish feed. The growth, mineral utilization and liver response of Clarias gariepinus fingerlings fed Toasted Lima Bean Meal (TLBM) diets supplemented with phytase was investigated. An Isonitrogenous diet (40% crude protein) was formulated with TLBM as a plant protein source. Phytase was added to diets post pelleting at 0 FTU (F1), 2500 FTU (F2), 5000FTU (F3), 7500FTU (F4) and 10,000FTU (F5). Feed were fed to triplicate groups of 15 fish (1.43 g ± 0.0012 g) stocked in 25 liter capacity plastic tanks, cultured at a mean dissolved oxygen, pH and temperature of 5.37mg/l, 7.2 and 25.8°C respectively for 56 days. Mean weight gain and Feed conversion Ratio (FCR) were significantly (P<0.05) higher in fish fed diets F3 and F4. Fish fed diets F4 had the highest Specific Growth Rate (SGR) 3.31, Protein Efficiency Ratio (PER) 1.78 and least FCR 1.41. The control (F1) gave the lowest SGR 2.79, PER 1.57 and highest FCR 1.6. There is increased phosphorus utilization with increased enzyme inclusion. Bone ash and phosphorus of fish showed mark increase with increasing level of phytase. Histopathological examination of fish revealed no negative effect of phytase on the liver of fish.