Grain legumes have great potential for improving smallholder farmers’ productivity in Sub-Saharan Africa (SSA) though their potential has not been fully exploited due to critical problems including high insect pests and disease infestation. As part of the process of addressing these challenges, the Collaborative Crop Research Program (CCRP) of the McKnight Foundation in collaboration with Cornell University and Kenya Agricultural and Livestock Research Organization (KALRO) recently introduced crop and soil enhancing strategies in Western Kenya. One of the strategies introduced included use of multipurpose grain legumes species in Nandi County (Koibem, Kapkerer and Kiptaruswo sites). Through this initiative, various legume species including common bean, cowpea, groundnuts, lablab and soybean of different varieties are being promoted at the farm level. However, no empirical study has assessed the economic benefits that farmers are likely to obtain if they adopt the legume species. In order to address the aforementioned knowledge gap, the present study sought to evaluate economic profitability from the production of grain legumes. Gross margins and profits were computed from farm-level data gathered from a random sample of 163 legume farmers in the above CCRP sites. Results showed that grain legumes species differed in terms of their gross margins; beans, groundnuts, cowpeas and soybean had positive gross margins while lablab had a negative gross margin. Further, the farm-area under grain legumes, age of the farmer, access to extension services and access to credit had significant influence on the amount of gross margin obtained by a farmer. The results point to the need for recruitment of more extension staff at local levels to enhance extension service delivery. Also, there is need for the county government to promote credit awareness and establish credit associations, which can boost farmers’ access to credit.