Abstract: Although the African Locust bean (Parkia filicoide) tree is widely distributed in Northern Nigeria, its application as an alternative replacement of conventional plant protein source in poultry feeds has not gained significant prominence. This study evaluates the inclusion level of fermented African locust bean seeds in broiler diets. One hundred and twenty Lohman broilers day old chicks were randomly divided into six experimental groups of two replicates each were used in a 9 weeks feeding trial to evaluate percentage of nutrients retained and serum indices of broilers. Dietary treatments were as follows: T1, T2, T3, T4, T5 and T6 representing 0, 25, 50, 75 and 100% replacement of groundnut cake replacement with fermented African locust bean seeds and 100% unfermented African locust beans. Treatment effects was significant (p<0.05) in the percentage of nitrogen, lipids, total ash, calcium and phosphorus retained. Crude fibre retention was not significantly (p>0.05) affected by experimental treatment. Treatment effect was significant (p<0.05) with fermented African locust bean seeds based groups giving better nitrogen, lipids and phosphorus retention with T5 showing best values. Nitrogen retention is positively (p<0.05) correlated with total serum protein, cholesterol, Hb/PCV and feed treatment (p<0.01); while crude fibre retention is negatively (p<0.05) correlated with all serum indices and treatment. Percentage retention of lipids is positively (p<0.05) correlated with total serum protein and cholesterol and so also with Hb/PCV and FALB inclusion at (p<0.01). Digestible ash is negatively (p<0.01) correlated with total serum protein and also negatively (p<0.01) correlated other serum indices and fermented African locust bean seeds inclusion at (p<0.05). Fermentation of African locust beans improved nutrient retention at both Gastrointestinal Tract (GIT) and portal system and availability for tissue synthesis.