Triggered by budgetary challenges and growing awareness of social needs, recent years have seen increasing entrepreneurial behaviour in the nonprofit sector, of which collaboration with for‐profit organizations is a case in point. Yet, while extant research has extensively studied the entrepreneurial orientation (EO) of for‐profit organizations, scant attention has been paid to its manifestations in the cross‐sector collaboration context and from the nonprofit perspective, even though numerous nonprofit organizations’ idiosyncrasies point to the need for a reconceptualization of the EO dimensions in that domain. Thus, taking the nonprofit perspective, our research aims to explore the dynamics and nature of EO in the context of nonprofit–business collaboration (NBC), examining how the EO core dimensions manifest themselves when nonprofit organizations (NPOs) proactively engage in NBC. We unpack the meaning of EO through two complementary empirical studies. Our work nuances the rather overlooked entrepreneurial posture of so‐called ‘active‐in‐collaboration’ NPOs, exposes new meanings of collaborative EO dimensions (relational proactiveness, relational innovativeness and relational risk management), discusses their underpinning mechanisms and suggests promising areas for further research and implications for practice.