This article examines the legal implications of Dr. Mohammad Mosaddegh’s actions in defending Iran’s sovereignty over the islands of Abu Musa, Greater Tunb, and Lesser Tunb, in the context of the doctrine of acquisitive prescription in international law. It first analyzes the legal framework governing the acquisition of territorial sovereignty, with a focus on the doctrine of acquisitive prescription—where continuous, peaceful, and unchallenged exercise of authority over a territory may, in limited circumstances, lead to a transfer of sovereignty. The article highlights the stringent conditions required for prescription to apply, emphasizing the necessity of uninterrupted and effective control by the occupying State and the absence of formal objections from the original sovereign. Through a detailed analysis of legal doctrine, international case law, and arbitral awards, it demonstrates that mere passage of time or unlawful occupation does not confer legal title. In this context, the study reviews Iran’s persistent and systematic protests against the British occupation of the islands, including diplomatic, administrative, and legal measures, with a focus on Mosaddegh’s tenure as Foreign Minister, Member of Parliament, and Prime Minister. It argues that Mosaddegh’s actions—such as formal protests, diplomatic communications, parliamentary advocacy, and administrative measures like the establishment of a civil registry on Abu Musa—constituted effective assertions of sovereignty, interrupting the temporal continuity required for acquisitive prescription. The study concludes that Iran’s legal and political efforts, successfully preserved its sovereignty over the islands and prevented the consolidation of British claims under the doctrine of prescription.