Introduction: The share represents the right of its holder on a part of the company, but it is distinct from the Joint ownership of a property. Although the nature of the right of the owner of securities is closer to the objective rather than subjective right, intangibility of the securities make it difficult to identify features and assess the quality of the securities for potential investors. This aspect of securities has resulted in imposing the duty to disclose the information on securities transactions on the primary and secondary market in some legal systems. In Iranian law, Securities Act of 2004 created the mandated disclosure system for securities transactions in the primary and secondary market. In this article, it is intended to examine if this duty is justifiable according to the special foundations of the Iranian legal system; and if yes, based on what foundations. In short, it can be stated that, given the special features and specific rules governing securities transactions, it is a significant imbalance between investors and powerful market participants in accessing to the information there, and it seems to be necessary to impose the duty to the disclosure of material facts on the stronger party...