Background and Objectives: Urban forests and green space contribute to human wellbeing. Green infrastructure is recognized by the European Union as a planning tool that contributes to the implementation of many public policies, with urban forests and green space as its main building blocks. Croatia and Slovenia are young democracies and recent members of the European Union. Hence, they also need to contribute to the implementation of those policies. Previous review studies on urban forests and green space rarely addressed scientific or professional publications in those countries. Furthermore, the body of knowledge about urban forest and green space research and practice in post-socialist countries is still rather weak. The goal of the paper is (a) to show that urban forest and green space research and practice is much stronger in these countries than it is possible to assume based only on previous review papers or only by searching Scopus and Web of Science, and (b) to describe publications written by scientists and professionals in the past 30 years. Materials and Methods: We used a trilingual systematic literature review to identify scientific and grey literature in various databases, as well as a snowballing technique, and yielded 211 publications in Croatia and 84 in Slovenia. Results: We identified many more publications on urban forests and green space science and practice in Croatia and Slovenia than it was possible to assume based only on previous review papers and when searching solely publications in English. Croatian authors showed continuity over time in terms of the number of publications, while Slovenian publications have been on the rise in the past decade. In both countries, scientific papers were most frequent, and the vast majority of studies addressed capital cities. Croatian publications mainly focused on parks and park forests, while Slovenian publications focused on urban forests. Interestingly, Croatian authors were affiliated with over 60 organizations, and in comparison to Slovenian authors, have a stronger preference towards publishing in their local language. Green space planning and design followed by resource inventory were the most frequent themes. The least addressed themes in both countries were resource management, economic aspects, policy, legislation, or governance. Conclusions: Important discussion in the future, especially in Croatia, would be the regulation of urban forestry as a profession. Cross-sectoral and interdisciplinary studies, as well as focusing on cities other than capitals in the future, can help in addressing issues such as climate change or the application of participatory approaches.