In this study L-glutaminase production by extremely halotolerant Halomonas elongata MM-5 using solid-state fermentation was investigated. Screening of a variety of agro-industrial byproducts such as rice husk, green gram husk, bengal gram husk, red gram husk, safflower oil cake, groundnut oil cake, black gram husk, groundnut skin and wheat bran was carried out individually and in different combinations. Optimization of various physicochemical parameters namely incubation time, pH, temperature, initial moisture content, carbon sources, nitrogen sources, L-glutamine concentration and inoculum level was carried out. Among the various substrates screened individually red gram husk supported the maximum production of enzyme 79.03±0.49 IU/gds. In the mixture of substrates screened red gram husk and bengal gram husk in the ratio (60:40) showed maximum 92.06±1.42 IU/gds enzyme production. The L-glutaminase production was maximum after 4 days of incubation period, pH 8, temperature 40°C and 80 percent moisture content. The lactose and malt extract used as carbon and nitrogen sources respectively supported the maximum yield of L-glutaminase. After screening and optimization of various parameters, the yield of L-glutaminase increased from 79.03 to 159.12 IU/gds.