This article analyses the struggle for possession of the House of Baha’u’llah in Baghdad during the 1920s and 1930s. One of the Bahai religion’s most sacred sites, the House of Baha’u’llah was the subject of protracted legal and political-diplomatic disputes following efforts by anti-Bahai activists to appropriate it from its Bahai custodians in 1921. The ensuing case touched almost every facet of the Iraqi judicial system, galvanised the international Bahai community and captured the attention of the British colonial state, the Iraqi government and the League of Nations. This article explores the causes and implications of the dispute, which can be considered one of the first incidents of religious persecution in modern Iraq. Rather than explaining the incident with reference to the intolerant attitudes of the Shi`i majority, the article argues for the role of the institutions of colonial modernity – the Mandates system, the new minorities regime, the praxis and discourse of colonial expansion, and the internationalism of the interwar period – for the unravelling of the case itself and for affecting modern, secular articulations of anti-Bahai prejudice.