Mutation breeding is one of the crop improvement technologies for boosting food security and sustenance of agriculture through important trait development. Among the food crops, legumes are important proteinaceous food sources of essential minerals and vitamins; however, they often exhibit low genetic variability due to the predominant habit of self-pollination. Significant breeding efforts have led to the development of improved mutant varieties. Progress in the area of mutation breeding in legumes has demonstrated that it offers great scope for achieving desired genetic variability and enhanced productivity, disease resistance, and nutritional quality. Mutant libraries have been developed for speedy and specific trait improvement. This chapter deals with methods applied in mutation breeding, detection of promising variants using different methods, and nondestructive selection approaches. Successful case studies are presented in which mutation breeding has resulted in trait improvement in legume cultivars, with a focus on nitrogen fixation efficiency, agronomic traits, and resistance to abiotic stresses. Further, this chapter highlights the value of mutation breeding as a practical tool for legume improvement, addressing the issues posed by climate change and the growing global demand for sustainable protein food supplies. The integration of modern genomics tools with breeding approaches can be considered as significant to improve the efficacy of mutant breeding approaches in developing improved germplasm in legume crops.