Herbivorous fishes play a key role in structuring coral reef ecosystems, yet how local benthic condition and broader seascape context interact to shape their distribution remains unclear. To address this, we used stereo remote underwater video systems to survey herbivorous fishes across island mangroves, back-reef, fringing reef, and isolated reef habitats in the inshore Great Barrier Reef, Australia, and quantify how benthic cover and seascape configuration shape herbivorous fish assemblages. Herbivores were recorded across all habitat types, demonstrating that many reef-associated herbivorous fishes use a range of habitats across coastal seascapes. Herbivore abundance was strongly and consistently associated with local benthic cover, particularly macroalgae and coral, indicating that resource availability drives herbivore abundance. In contrast, functional richness was highest in more diverse and well-connected seascapes, highlighting the role of habitat composition and configuration in supporting a broader range of herbivore roles. When combined into a herbivory potential index (combining abundance and functional richness), values were highest in habitats with high benthic cover and in more diverse, well-connected seascapes. These findings show that interacting local and seascape-scale processes shape herbivore assemblages, highlighting the importance of conserving both benthic resources and diverse, well-connected seascapes.