A 6-week feeding trial was conducted to evaluate the potential to use sweet potato and soy sauce by-product as an ingredient in the diet of Oreochromis niloticus juveniles. Five experimental diets D1-D5 were formulated with 0, 10, 20 and 30% sweet potato, and a mixture of 10% soy sauce by-product and 20% sweet potato, respectively. A commercial extruded pellet diet was used as the control (D6). O. niloticus juveniles with an initial weight of about 3 g were reared in 30 l aquariums illuminated by overhead fluorescent lights to maintain a constant photoperiod of 12 h light and 12 h dark cycle. Water temperature was maintained at 25±0.5°C. The control commercial diet showed the best growth performance. Among the formulated experimental diets, D1 had the best growth performance and D5 had the lowest growth performance in terms of the growth parameters measured. Whereas there was no significant difference between D2 and D3, but the performance in both diets was much better than D4 and D5. These results demonstrated that a 10-20% inclusion of sweet potato meal could be used as a replacement of wheat meal in practical diets for juvenile O. niloticus. With an appropriate recycling method, soy sauce by-product can be used as a fish food ingredient if the offensive odours are removed.