Different fungal isolates were screened for the production of mannanase under solid state cultivation at static condition. Penicillium italicum LAD-A5 was selected as the most potent in producing enzyme of high activity. It was therefore selected for further studies. The nutritional requirements of Penicillium italicum LAD-A5 for the production of mannanase in solid state fermentation were investigated. The process parameters optimized include; carbon and nitrogen sources, inoculum concentrations, percentage moisture content and sugar supplementation. Utilization of different agrowastes on mannanase production was evaluated. Orange peels were found to be the most effective carbon source with highest mannanase activity of 129.130 U/ml. Yeast extract meal was obtained to be the best nitrogen source with highest activity of 128.380 U/ml out of all the nitrogen sources screened in this study. The best percentage moisture content for maximum enzyme activity was obtained at 50%. Inoculum concentration of 1×106 yielded highest mannanase activity of 37.562 U/ml. Addition of simple carbon sources to medium containing locust bean gum caused a slight catabolic repression of mannanase synthesis.