Early Judaeo-Persian (EJP) is the form of Persian that was spoken by Jews, and written in Hebrew script, in ca. the 8th-12th centuries C.E. Most EJP manuscripts have been found in the Cairo Geniza from the late 19th century onwards. Since the dialectal basis of EJP is different from the Early New Persian (written in Arabic script) that was spoken in north-east Iran at the same time, the study of EJP is essential for an understanding of the development of New Persian. So far, only isolated grammatical features of EJP have been studied. The present work is the first attempt at a comprehensive description of EJP grammar in its own right, based on the study of the most important EJP texts, published and unpublished.