Grain legumes play a crucial role in global food security as rich sources of protein, carbohydrates, minerals, and vitamins. Despite their nutritional value, grain legumes remain underutilized compared to major cereals. This chapter explores the challenges and opportunities in breeding underutilized grain legumes to enhance their productivity and nutritional quality. This chapter highlights the nutritional importance of grain legumes and their potential to contribute to global food and nutrition security. It discusses the factors limiting their widespread adoption, including low yield, susceptibility to pests and diseases, and limited genetic diversity. The recent advances in grain legume breeding, with a focus on innovative approaches to improve yield, disease resistance, and nutritional content, is reviewed. It examines genetic studies on qualitative and quantitative traits, breeding objectives, and the progress made in varietal development through conventional and modern approaches, including marker-assisted breeding, genomic tools, CRISPR-Cas technology, and de novo domestication. It discusses the application of genomic tools, participatory breeding, and molecular marker-assisted selection in accelerating the development of improved varieties. Finally, the research priorities and future directions for underutilized grain legume breeding are identified, and it emphasizes the need for collaborative efforts among researchers, farmers, and policymakers to promote the wider adoption of these crops.