Between the adoption of the statute of an international organization and the time it enters into force, and the organization is formally established, numerous preparatory measures must be undertaken to ensure the swift and effective commencement of its activities. This responsibility is typically assigned to a Preparatory Commission. However, due to the limited attention given to the legal status of such commissions in international law, several questions may arise: How are these bodies formed? What responsibilities are delegated to them? What powers do they possess? Are Preparatory Commissions considered subsidiary organs of the future organization, or do they enjoy a distinct legal personality? This article aims to explore these issues in light of contemporary international practice, with particular reference to the establishment processes of several major international organizations.