Urbanization and anthropogenic development have fundamentally altered ecosystem dynamics on a global scale. Conservation and management of comparatively less modified landscapes adjacent to highly modified landscapes requires careful consideration of interactions between landscape types. Restoration or conservation of habitat within a developed matrix is generally thought to have beneficial effects on landscape-level ecological processes. We propose an ecological spillover framework to critically assess how restoring or conserving species populations within anthropogenically modified landscapes may affect adjacent wildland populations. Within the framework, the spillover process is divided into seven interconnected 'nodes', which identify points at which potential cause-effect relationships may exist between urban and wildland populations. The framework is useful for a wide range of project-specific ecological relationships, and can help scientists and managers identify knowledge gaps and weigh risk in conservation decision-making. We queried the conservation literature to identify research focused on the impacts of urban species populations on regional wildland populations. Our search revealed seven ecological processes that have the potential to be affected by urban to wildland spillover and we found relatively few studies that explicitly analyze spillover effects from urban to wildland areas. Organisms living in urban areas within restored or remnant habitats located in an urban matrix, or within the built environment have largely unknown effects on landscape-level ecological processes. We conclude with a discussion on the critical gaps in research linking these habitats to larger landscape-level ecological understanding, and provide recommendations for research priorities that might illuminate this important aspect of 21st century conservation planning.