This study tested the potentials of dietary Chlorella vulgaris (CM) as a replacement for soybean meal (SBM) on the growth, nutritional performance and histology of the liver in the diet of Genetically Male Tilapia (GMT) Tilapia, Oreochromis niloticus. One hundred and eighty fish averaging 6.00 g were randomly stocked into 12 individual 30 -L flow-through tanks. Four isonitrogenous and isocalorific experimental diets were formulated to contain 38 % crude protein and 9 % lipids in which Chlorella vulgaris was used to replace soybean meal.  The control was made up of fish meal (FM) which supplied 100% of the dietary protein; soybean (SBM) supplied 100% of the dietary protein in diet 2. Chlorella vulgaris was used to replace soybean meal at 50% and 100% in diets 3 (SCM) and 4 (CM) respectively. After the 5-wk feeding trial, the growth, nutritional performance and histology of the liver fish from each tank were assessed. Significant improvement  were observed in survival, feed intake and liver histology of fish fed chlorella based diet SCM and CM, however the control had significantly better weight gain (0.79gram/day ±0.63) and  feed conversion ratio (0.93 ±0.07) at the end of the 5-wk feeding trial (p>0.05). The cumulative mortality of fish fed the SCM and CM diets was significantly lower (p>0.05) than that of fish fed the FM and SBM diet at the end of the experiment. Chlorella vulgaris seemed to be an effective potential replacement for soybean meal for required growth, and good health of tilapia, Oreochromis niloticus.