The early Mongolian writing system was similar to that of Old Uygur in terms of pronunciation, orthographic rules, and the arrangement of lines. Therefore, it has also been known as the Uygur-style Mongolian script. The earliest existing example of this is the inscriptions on the Esunge Stele of 1225. In the 17th century, the Mongolian writing system evolved into two branches: the modern Mongolian script popular among most Mongolian communities, and the Todo script used only by speakers of the Oirat dialect.

The modern Mongolian script, with an alphabet of 29 letters, boasts several improvements over its predecessor: the shapes of its letters have been improved to make continuous writing easier; letters for spelling loanwords have been added along with modern-style punctuation; and the practice of segmenting words has been ended. The Todo script was created in 1648 by the Oirat Buddhist monk Zaya Pandita Namkhaijamts (Oktorguin Dalai) specifically for the Oirat dialect. With 31 letters that differ slightly in shape and pronunciation from their equivalents, if any, in the modern Mongolian script, it better fits the phonology of the Oirat dialect. In 1945, Mongolia changed its official writing system into the Cyrillic script (commonly known as the new Mongolian script). Based on the Cyrillic script, it features two additional vowels and utilizes double letters to express long vowels.