Iran is a mosaic of six major ethnic groups—Turkic, Kurdish, Arab, Baloch, Turkmen, and Lur—and numerous minorities. This diversity enriches national culture but can generate socioeconomic and security challenges when ethnic policies are inadequate. This study conducts a comparative analysis of ethnic policies before and after the Islamic Revolution (Pahlavi I, II, and the Islamic Republic) through library research and a systematic review of historical, legal, and scientific sources. The theoretical foundation combines Martin Rogers’ assimilation–multiculturalism models with Zandi’s “unity in diversity” approach. During the Pahlavi era, forced Persianisation, political centralisation, and repression—including resettlement and suppression of local languages—provoked lasting grievances and uprisings. The post‑1979 Constitution introduced a hybrid model merging multicultural guarantees (freedom of language, religion, and culture) with national convergence (citizen equality and participation). Yet implementation has varied across political coalitions—reformists, principlists, and moderates—shifting between security‑centred approaches in wartime, developmental strategies, and decentralisation efforts. All faced persistent obstacles: weak law enforcement, regional disparities, and external manipulation of ethnic tensions. Although Iran’s constitutional framework affirms equality and diversity, inconsistent execution and fluctuating political narratives have hindered national cohesion and occasionally intensified divergence. Sustainable integration, therefore, requires a coherent “unity in diversity” strategy ensuring linguistic and cultural rights, inclusive local governance, and equitable economic distribution