With increasing population growth, sustainable waste management remains a global challenge. This study evaluated the effects of using defatted black soldier fly larvae meal (BSFLM) instead of fishmeal (FM) on the growth performance of Nile tilapia (Oreochromis niloticus). The black soldier fly larvae were reared using fecal sludge and organic waste as substrates, harvested at the prepupal stage, and then defatted. Three isonitrogenous diets (30% crude protein) were formulated in which BSFLM substituted FM at 0% (control, diet 1), 50% (diet 2) and 100% (diet 3) on a protein basis. A 90-day feeding trial was conducted using 270 Nile tilapia fingerlings (9.62 ± 0.22 g) in a completely randomized design. The fingerlings were distributed into three groups of three replicates (30 fingerlings per net hapa). There was a decrease in final body weight (47.73, 42.98 and 34.57 g) with increased substitution of BSFLM for diets 1, 2 and 3, respectively (p = 0.018). Diet 2 exhibited the highest survival rate (95.56%). The economic profit index recorded for diets 1 and 2 was not significantly different. Based on these results, BSFLM can effectively replace fish meal by 50%, with no detrimental effect on growth