The Mahāratnakūṭa is a collection of Buddhist texts, the bulk of which belong to the early Mahāyāna tradition. Its extant versions are included in the Chinese Tripiṭaka as well as the Tibetan and Mongolian Kanjurs. The collection has been studied to a certain extent with the use of the Chinese and Tibetan sources but almost nothing is known of its Mongolian-language versions. The article aims to provide a preliminary study of the Ratnakūṭa in the Mongolian manuscript Kanjur compiled in 1628–1629. It examines the structural traits of the collection, the data of the colophons and some textual elements preserved from the Tibetan original/s. The analysis reveals that, possibly, the major part of the Ratnakūṭa or the whole collection was translated into Mongolian en bloc in 1628–1629. The collection lacks eight sutras and places the final forty-ninth work between texts thirty-five and thirty-six. A number of textual elements preserved from the Tibetan source/s point to the proximity and possible relation of the Mongolian Ratnakūṭa to the Them spangs ma and Western Tibetan Kanjurs.