To compare the seed productivity of germplasm in India (Tamil Nadu) and Japan (Tsukuba), a total of 105 accessions from the Japanese National Agriculture and Food Research Organization (NARO) sorghum core collection were cultivated. The comparative cultivation studies were conducted at two locations in India and one in Japan. Differences in cultivation environments, including day length, temperature, and rainfall were evident in all the studies, and accordingly, seed production varied. The accessions grown in Japan yielded the highest number of grains per panicle. However, 11 accessions cultivated in Japan produced no harvest. Conversely, all accessions grown in parts of India, such as in Coimbatore, produced seeds. Therefore, although seed production in Japan was superior, there were benefits to cultivating the crops in India, including longer cultivation periods and the ability to overcome difficulties with seed multiplication found in Japan. Comparative cultivation projects involving international collaborative research are essential to reveal seed productivity in genetically diverse resources of sorghum. This study provides data about international sorghum production and information about differences in available accessions.