Leveraging big data in the mobility sector can help address some of today’s most significant challenges, from enhancing sustainability to optimizing mobility services and improving the quality of life for users. However, despite the recognized potential of data sharing to generate social impact, those entering data sharing partnerships often express concerns regarding cost-benefit uncertainties, data use risks, and the operational and organizational challenges associated with collaboration. Our research adopts a collaborative perspective on data sharing, investigating how perceptions of the benefits and risks influence participation strategies in such partnerships. We conducted empirical research within the context of the European project MobiDataLab, which aims to prototype new solutions for mobility data sharing, increasing data sharing culture. This study involved collecting archival data and conducting semi-structured interviews with key actors in the transport sector, analyzed using the grounded theory approach. Our findings underscore the role of trust and satisfaction in shaping attitudes toward data sharing and behaviors within large cross-sectoral partnerships. These attitudes and behaviors are influenced by perceptions of data sharing risks and opportunities, leading to varied satisfaction levels with the status quo and trust in data sharing processes and partners. These factors, in turn, pave the way for three attitudes and corresponding data sharing strategies: refraining, improving, and maintaining. By elucidating how different attitudes and beliefs regarding data sharing impact strategies at the partnership level and thus influence a partnership’s trajectory and outcomes, we contribute to the literature on cross-sectoral partnerships and the collaborative dynamics of data sharing.