Effects of microbial inoculant on composting process and improvement of nutrient values in fish waste compost were assessed through a field study. Heavy metals and plant growth bioassay using various degrees of maturity of compost products were evaluated to determine their environmental acceptability and product quality. All of the heavy metals (Cd, Cr, Cu, Pb, Zn, Hg) are well below the regulatory limit for compost application on crops. A bioassay based on growth and nitrogen content of annual ryegrass, perennial ryegrass, jubille sweet corn and marigold as well as biomass and phosphorous content were well correlated among the parameters. Seed germination assays showed microbial inoculants applied in two types of compost had consistently enhanced germination and root elongation of four crop seeds. The use of selected microbial inoculant in composting putrescible materials such as fish wastes and further stabilization of lignocellulosic wastes has been demonstrated as a useful tool to modify the physical and chemical characteristics by improving nutritional status and changing the mineralization and humification processes. Results reveal that these compost products have significantly improved agricultural and horticultural commodity value when applied to soils at optimal rates.