Abstract This article provides novel insights into the main factors associated with integration policies at the national level. Existing literature has analysed specific factors in Western countries, while a comprehensive, theoretically informed, and up-to-date overview is missing, especially regarding non-Western countries. This article fills this gap by combining 2014 and 2019 Migrant Integration Policy Index data on integration policies in 56 countries—including non-Western countries—with publicly available international data on migration and asylum trends, economic conditions, and public opinion on migration. Building upon existing literature, we introduce three perspectives: evidence-based, institutionalist, and partisan perspectives. The evidence-based perspective assumes that policy-makers act based on objective factors related to the policy issue (e.g. the number of migrants). The institutionalist perspective points to the relevance of institutional conditions, such as labour markets and welfare institutions. The partisan perspective refers to the role of political ideologies and attitudes in public opinion and in the media. Results suggest that factors related to the institutionalist perspective play the most critical role, alongside factors linked to the partisan perspective. However, the results provide evidence for all three perspectives. Migrant integration policies are associated with several factors: the number of asylum applications and the number of refugees (evidence-based perspective); GDP (per capita) and welfare expenditure (institutionalist perspective); political ideology; and public opinion (partisan perspective).