Cover crops have been part of sustainable agriculture movements. The potential use of mung bean (Vigna radiata L. Wilzeck) as a cover crop and its effect on soil organic carbon and maize yield were explored in this study. Six cover crop treatments; 250,000 plants/ha desiccated at 28 days after sowing (DAS),  250,000 plants/ha desiccated at 35 DAS, 375,000 plants/ha desiccated at 28 DAS, 375,000 plants/ha desiccated at 35 DAS, 500,000 plants/ha desiccated at 28 DAS, 500,000 plants/ha desiccated at 35 DAS and one control treatment (without cover crop), were tested in a semi-arid area of North Lombok, West Nusa Tenggara. Maize seeds at a population density of 98,000 plants/ha were planted two weeks following the desiccation times. The treatments were arranged in a Randomized Block Design with three replications. The results revealed that the higher cover crop population density coupled with the later desiccation time, the higher the above ground biomass produced, being the highest at 8.3 Mg/ha and the lowest at 2.6 Mg/ha. The highest cover crop biomass improved soil organic carbon content by 60%, nitrogen, phosphorous and potash concentrations in maize plants tissue by 54%, 54% and 63%, respectively at tasseling, compared to those plants in the control treatment. Maize yield increased by 24%, being 7.24 ton/ha at the control treatment and 8.95 ton/ha at the highest cover crop population density desiccated at 35 DAS. The use of mung bean as a cover crop sounds promising and further studies are needed to explore more of its potential benefits.