Exploring alternative feed ingredients is essential to find an equivalent substitute for maize in Kamang duck diets, thereby reducing feed costs. Cassava waste, i.e. a mixture of fermented cassava peel and leaves (FCPL) using a novel bacterium Citrobacter freundii 5519, shows potential as a maize replacement. The present study evaluated its effects on the performance and meat quality of Kamang ducks. A total of 100 three-week-old male Kamang ducks were divided into 20 experimental groups and reared for five weeks. A completely randomised design (CRD) with four treatments and five replications was employed. The data were analysed using ANOVA, followed by Duncan’s multiple range test (DMRT) for significant differences. Parameters under study included performance, internal organs, and meat quality. The results demonstrated that incorporating FCPL as a maize substitute at levels up to 45% significantly increased feed intake, weight gain, and carcass percentage (P < 0.05), while markedly reducing abdominal fat, meat fat, and cholesterol (P < 0.05) compared to the control group. However, no significant effects were observed on the weight of digestive organs (P > 0.05). Utilising FCPL as a 45% maize substitute improved performance and meat quality without negatively affecting the digestive organs of Kamang ducks.