Although present research shows that ambitious corporate sustainability objectives improve employee engagement in business organizations, there is scarcity of research showing how employees engage in corporate sustainability objectives and become autonomous sustainability thinkers. We suggest that a strong, individual level of psychological ownership of corporate sustainability is a precondition for the development of sustainability thinking, and examine the factors that influence the emergence of such feelings of ownership. Our qualitative study, based on 29 interviews conducted in seven Finnish local business (...) units from three different technology-oriented multinational enterprises (MNEs), shows that several key factors can have contradictory effects, both strengthening and hindering the routes to psychological ownership of corporate sustainability. While these contradictory effects may potentially lead to confusion among employees, our findings may help managers to avoid pitfalls in developing a more sustainability-oriented organizational culture. Moreover, by applying the theory of psychological ownership, our study contributes to the business sustainability research by providing new theoretical opportunities to understand the process of how individuals may become engaged in enhancing business sustainability. (shrink)