Ethnic diversity is one of the important features of Iran's social and cultural structure, and the way policymakers deal with it can affect cultural identity, social justice, ethnic participation, and national cohesion. The present study aimed to examine the impact of ethnic diversity on Iran's cultural and social policies from the 1990s to the 2001s. This study was conducted with a qualitative approach and documentary method and content analysis of official documents, including the approvals of the Islamic Consultative Assembly, the Supreme Council for the Cultural Revolution, the Cabinet of Ministers, the five-year development plans, and the details of the parliamentary negotiations. Five indicators of cultural identity and diversity, justice and non-discrimination, ethnic participation, language and cultural heritage, and national cohesion were used to analyze the policies. The findings show that in the 1990s, the policy-making approach was mainly unity-oriented and focused on managing ethnic differences within the framework of national identity; in the 2000s, attention to identity, cultural demands, and regional development increased; and in the 2011s, cultural diversity, cultural justice, indigenous heritage, and social participation became more prominent in official policies. Despite these changes, the emphasis on Islamic-Iranian identity, the Persian language, and national cohesion has continued throughout the three decades. Overall, rather than fundamentally changing policy principles, ethnic diversity has led to a modification and expansion of attention to indigenous cultures, cultural rights, regional justice, and social participation. Accordingly, the dominant pattern of Iranian cultural policymaking can be considered