This paper discusses the status of the Ezafe particle -(y)e in Persian and provides an affixal analysis of the Ezafe, formalized within Head-driven Phrase Structure Grammar (HPSG). The Ezafe, a feature of certain Western Iranian languages, is realized as an enclitic and links the head noun to its modifiers and to the possessor NP. The latter follow the head and are linked to one another by the Ezafe. On the basis of crucial empirical facts that have never been discussed in previous studies, I argue that the Ezafe is best regarded as an affix attaching to nominal heads (nouns, adjectives and some prepositions), as well as to nominal intermediate projections, and marking them as expecting a modifier or a direct nominal complement. Viewed as such, the Ezafe construction is an instance of the head-marked pattern of morphological marking of grammatical relations. This analysis differs from all previous accounts of the Ezafe (i.e. as case-marker, syntactic or phonological linker) and entails that the Ezafe, which originated in the Old Iranian relative particle -hya, has undergone a process of reanalysis-grammaticalization, to end up as a part of nominal morphology.