Learning is considered a means to achieve sustainability in practice and has become a prominent goal of sustainability interventions. In this paper we explore how learning for sustainability is shaped by meaning, interpretation and experience, in the context of UNESCO Biosphere Reserves (BRs). The World Network of Biosphere Reserves brings environmental conservation, socio-economic development and research together in 'learning sites for sustainable development.' The World Network is globally significant, with 669 BRs in 120 countries, but as with many paradigmatic sustainability interventions BRs are perceived to suffer from a 'concept-reality gap.' We explore this gap from an interpretive perspective, focusing on participant interpretations of the meaning of BRs and their experiences of working with the concept - with the aim of painting a richer picture of learning for sustainability and the ways in which BRs might fulfil their role as learning sites. We provide a cross-case analysis of learning in 11 BRs around the world, drawing on interviews with 177 participants, and ask: How is the BR concept interpreted and enacted by people involved with BR work? What learning emerges through BR work, as described by those involved? We find that the BR concept is interpreted differently in each location, producing distinct expectations, practices and institutional designs. Learning occurs around common themes - human environment relationships, actors and governance arrangements, and skills to navigate BR work - but is expressed very differently in each BR. The position of BRs 'in between' social, ecological and economic goals; local places and global networks; and government, private and civil society sectors, provides a valuable space for participants to learn to live with social-ecological complexity. We discuss our results in terms of their contribution to three pressing concerns in sustainability science: (i) power and politics in learning for sustainability, (ii) intermediaries and bridging organizations in multi-level governance, and (iii) reflexivity and knowledge action relationships. Our comparative hermeneutic approach makes a novel methodological contribution to interpretive studies of sustainability policy and governance.