The Iranian Constitutional Revolution is considered one of the most important political developments in contemporary Iranian history. In the meantime, England's policy towards the Constitutional Revolution has a special place, because Britain was simultaneously seeking to preserve its colonial interests in Iran and contain the influence of Tsarist Russia. This research aims to examine England's policy during the Iranian Constitutional Revolution and analyzes the goals, tools, and consequences of London's approach to Iranian political developments. The main question of the article is why and how England supported some constitutional movements and at the same time supported the limitation and control of the revolution at different stages. The theoretical framework of the research is based on Walt's realist approach to international relations, which considers the behavior of states to be subordinate to national interests and the balance of threats. The research method is descriptive-analytical and the data were collected based on library sources and historical documents. The research findings show that England's initial support for the Constitutionalists was more in line with preserving the country's geopolitical interests and preventing the expansion of Russian influence in Iran than in terms of a commitment to freedom and democracy. The Constitutionalists' blockade of the British embassy, ​​political and media support for some Constitutionalist leaders, and efforts to influence the power structure of Iran were part of England's policies during this period. However, after the conclusion of the 1907 agreement between Russia and England and the division of Iran into spheres of influence, London's policy shifted toward controlling and limiting the Constitutionalist movement. As a result, England's policy in the Constitutional Revolution should be considered a pragmatic policy, based on colonial interests and subject to the competition of great powers, which had a profound impact on the course of political developments in Iran.