This paper proposes and then tests a cross-level model pertaining to the intrapersonal and collective antecedents of work-related proactive behaviors. The model posits individual-level positive relational experiences and unit-level relational coordination as social contextual antecedents of individual-level proactive behaviors. The effects of these mechanisms are hypothesized to be mediated respectively by individual-level role breadth self-efficacy and unit-level psychological safety climate. To test the proposed model, multi-source data were collected from a representative sample of 246 staff nurses and their respective unit managers, based in four privately owned hospitals. Supporting evidence for the model enriches understanding of the role of social context in variously enabling and undermining the expression of proactive behaviors on the part of individuals, suitably aligned with the wider needs of key organizational units, in safety-critical work environments. We discuss the implications of our findings for fostering such behavioral alignment and outline directions for future research.