It has generally been argued that Persian does not include dummy elements called expletives, in spite of the existence of the morpheme ǐn which shows the behavior of an expletive in specific constructions. The morpheme is not a part of the argument structure and has no meaning. In Persian, which is a pro-drop language, the morpheme ǐn as expletive is generated only in [SPEC CP] of an independent clause. This element may occur in a subject position, object position, or as an object of a preposition. In subject and object positions it is optional when S′ moves to the end of the sentence, or is adjoined to it, in other cases it is obligatory. As an object of a preposition it is always obligatory, no matter whether the structure is the result of a movement or not. The aim of this article is to provide evidence in favor of the existence of expletives, and their projection in Persian.