The Constitutional Revolution is one of the most significant events in Iran's political history, and its consequences have, directly or indirectly, influenced all political, economic, and social developments in the country over the past 120 years. Consequently, analyzing and tracing the roots of this event's various dimensions, including the factors behind the revolution's victory and the instability of the political system that emerged from it, remains relevant and is of great importance in the present era. This major event was influenced by numerous domestic and foreign factors. The British Empire, commensurate with its position in the international system and its level of influence in Iran during that period, also played a role in shaping the Constitutional Revolution and its outcome. The present research seeks to examine and analyze the diverse actions and positions of Britain during the Iranian Constitutional Revolution. The research method is descriptive-analytical; data was gathered using documentary analysis and is analyzed using a narrative analysis approach. According to the research findings, the British played a role in all stages of the Constitutional Revolution and the resulting political system. Britain's stance towards the revolution and the constitutional government comprised three distinct phases: 1) Covert and overt support; 2) A shift in position and withdrawal of support for the constitutional movement following the 1907 Convention with Russia; and 3) Direct intervention in the suppression and overthrow of the constitutional political system. These contradictory positions can be analyzed and evaluated within the framework of the country's realist foreign policy, its colonialist nature, and the ineffective governance in Qajar-era Iran.