Proso millet is an important short-duration crop that adapts well to varied climatic conditions and is grown worldwide for food, feed, and fodder purposes. Proso millet is used for feeding birds as livestock feed in developed countries and for food in some parts of Asia. Nutritionally, proso millet grains are rich in protein, vitamins, minerals, and micronutrients including iron, zinc, copper, and manganese, compared to other staple cereals. A diversity set consisting of 200 accessions was formed, and this set included 106 accessions of core collection, originating from 30 countries, representing five races of proso millet (60.5% miliaceum, 12.5% each of compactum and contractum; 8.5% patentissimum and 6.5% ovatum). These accessions were selected using the cluster information of proso millet which was used to assemble the core collection. This set represents 24% of the entire collection and 22 to 27% of each race of proso millet germplasm conserved at the ICRISAT Genebank. This set can be an ideal diversity set for initiating proso millet improvement program, and also genetic investigation and allele mining. This set was characterized for agronomic and grain nutrient content in the 2015 and 2016 rainy seasons at ICRISAT Patancheru, India, and trait-specific germplasm sources were identified.