Urban gardens are spreading in many cities across Europe, with community gardening being a fundamental form of urban agriculture. While the literature reveals the essential role that community gardens can play in terms of learning and education, no studies have investigated the training needs for participants in community gardens to ensure their successful development. The goal of this article is to evaluate the training requirements of urban community gardens to ensure their successful implementation and their contribution to sustainability in European cities. Two questionnaires of users’ needs analysis were designed and implemented in Berlin, Bologna, Budapest, and Cartagena. The results unveiled the need to re-enforce the training in the formation and community building phases of community gardens towards ensuring the creation of an engaged gardening community to maintain activity, particularly for top-down activities (e.g., research-related gardens). Users claimed their need for being trained on crop management skills (e.g., maintenance, bed preparation, organic practices) and on communication skills to further disseminate their activity, thereby increasing the potential for citizen engagement. Such requirements could be overcome with the creation of urban gardens networks, where experiences and knowledge are shared among practitioners. Policy recommendations are provided based on the outputs of this study.