The exploration of alternative protein sources in feed has become imperative to reduce dependence on conventional protein sources such as fishmeal (FM) using Black Soldier fly, Hermetia illucens Lin. (BSFLM), as substitute. Therefore, the aim of this study was to investigate the growth response of dual purpose grower chickens fed diets with varying levels of inclusion of defatted BSFLM. The experiment was conducted using 2 X 5 factorial arrangement in a randomized complete block design. 600 birds comprising of 300 FUNAAB Alpha® and 300 Noiler 10-week old dual purpose birds previously raised in a deep litter pen were randomly assigned to five dietary treatments with six replicates containing ten birds each. The study lasted for 9 weeks during which the growth indices of the birds were investigated. Five isocaloric and isonitrogenous grower diets comprising of control diet (basal diet with 3% fishmeal without defatted BSFLM inclusion) and basal diets with one of the four levels inclusion of BSFLM (25%, 50%, 75% and 100%) as protein for protein replacement for FM were fed ad-libitum. The body weight and feed intake (FI) of the birds were assessed and recorded weekly, while the FCR were calculated. Data obtained were subjected to one way Analysis of variance using SAS (1999). Significant means were separated using Duncan’s multiple range test. Interactive effect (P<0.05) of Breeds and levels of inclusion of BSFLM were observed on the final weight (FW), body weight gain (BWG), FI and FCR of the birds. Birds fed diets containing 50% BSFLM and fish meal had significantly (P<0.05) higher FW, BWG and FI compared to birds fed other diets. Birds fed diet with 100% BSFLM had significantly (P<0.05) higher FW and BWG (2698.08g/bird;1349.00g/bird) relative to those fed control diet (2553.83 g/bird; 1200.83 g/bird). The feed efficiency of the birds reduced linearly (P<0.05) with increasing BSFLM.