Abstract Urban green spaces (UGS) provide mechanisms through which people connect and interact with each other, strengthening social relationships as well as human‐nature connections, both of high relevance for sustainable development. However, what determines urban residents' engagement in activities for the protection of UGS still lacks a systematic understanding. Our study aims to address this gap by enriching the value‐belief‐norm (VBN) theory with relational values based on a questionnaire (N = 221) among residents engaging in UGS maintenance in the city of Munich (Germany). Exploratory factor analysis and structural equation modelling showed that both individual responsibility and societal responsibility guide urban residents in their actions towards UGS protection. Furthermore, we found a direct impact of biospheric, altruistic and hedonic values on engagement for the protection of UGS. Therefore, this study signals the importance of investing in actively promoting pluralistic values among urban residents as cities today urgently need a reconnection of the human‐nature relationship and UGS stewardship actions. As we further confirm that relational values have impact on the constructs of the VBN theory, we conclude with a plea for recognizing the potential of relational values as enablers of change towards more responsible behaviours towards urban nature. Read the free Plain Language Summary for this article on the Journal blog.