The influence of cooked African walnut flour substitution levels in the proportion of 100:0, 95:5, 90:10, 85:15,80:20 on nutrient composition of muffin was investigated. The composite flour was produced and then analyzed for proximate properties. Muffin was produced from the composite flours and analysed for nutrient composition. All data generated in the study were analyzed statistically. Results of the composite flour showed that moisture content, ash and fat varied between 9.68 and 15.20%, 1.30 and 3.52%, 1.82 and 45.34%, respectively, for wheat flour and cooked African walnut samples; likewise, crude fiber, protein and carbohydrate were 1.00 and 1.14%, 10.34 and 24.13, 74.09 and 15.38% correspondingly. Muffin sample indicated increasing level of moisture, protein, fat and crude fibre while there was decrease in carbohydrate as the proportion of cooked African walnut flour increases. Values obtained showed that moisture content increased from 9.68-24.17% with the highest and lowest moisture content observed in sample T0 and T4. Ash, fat,  crude fibre and protein content also increased from 1.30-1.88%, 1.82-19.54%, 1.00-1.68% and 10.34-22.44% respectively, for muffin produced from 100% wheat flour and muffin from different blends of wheat- cooked African walnut flour. However, carbohydrate content decreased from 74.11- 54.66-% respectively, for muffin from 100% wheat flour and muffin made using different blends of wheat- cooked African walnut flour. The study showed muffin produced using T4(80:20 wheat- cooked African walnut flour) was better in terms of nutrient composition and can be recommended for commercial production of muffin.