<p>Urbanization is a major threat to global biodiversity because it alters environmental conditions at both local and landscape scales. As urbanization accelerates, understanding its effects on biodiversity has become increasingly important. Ants play key ecological roles and are reliable bioindicators, making them useful models for assessing biodiversity responses in cities. The aim of this study was to investigate how ant communities in urban squares are affected by local site characteristics of the squares and by their surrounding landscapes in Rio de Janeiro, Brazil. Ant diversity (Hill numbers) was calculated for different groups of ant species: all native, native arboreal, native leaf-litter and non-native species. To investigate the effects of local and landscape characteristics on ants, an information-theoretic model selection framework was employed. Results indicate that ant diversity in urban squares is structured by environmental filters operating at multiple spatial scales. Local vegetation structure emerged as a strong filter: canopy cover had a consistently positive effect on native ant diversity in all evaluated groups. Additionally, the surrounding landscape played a key role in shaping ant diversity in urban squares: urban cover had a negative effect on native arboreal and leaf-litter ants but also on non-natives, forest cover had a positive effect on native arboreal and non-native ants and forest fragmentation had a positive effect on total and arboreal native ant diversity. These findings suggest that ant diversity in urban squares can be enhanced by increasing canopy cover and the amount of urban green spaces interspersed among built-up areas in the city.</p>