Because Mozarabic was not a language of high culture, it had no official script. Unlike most Romance languages, Mozarabic was primarily written in the Arabic alphabet rather than the Latin alphabet, though it was also written in the Latin alphabet and less so in the Hebrew alphabet. Most documents were in the Arabic alphabet. Mozarab scholars wrote words of the Romance vernacular in alternative scripts in the margins or in the subtitles of Latin language texts (glosses).

The two languages of culture in Medieval Iberia were Latin in the north (although it was also used in the south by Mozarab scholars) and Arabic in the south (which was the principal literary language of Mozarab scholars). These are the languages that constitute the great majority of written documents of the Peninsula at that time.

Mozarabic is first documented in writing in the Peninsula as choruses (kharjas) (9th century) in Arabic lyrics called muwashshahs. As these were written in the Arabic alphabet, the vowels had to be reconstructed when transliterating it into Latin script.