In order to respond to key challenges in safety and security, individuals and organisations must often collaborate across workplace boundaries, working with people and organisations from different nations and sectors, and with different disciplinary/functional backgrounds. However, research suggests that these kinds of relationships are often fraught with ingroup versus outgroup divisions, which disrupt coordination and hamper operational performance. Against this backdrop, this chapter takes an identity perspective to shed light on the causes of these divisions and potential solutions that may facilitate better relations and cooperation across workplace boundaries. The chapter incorporates recent academic literature in the safety and security domain as well as relevant empirical research to provide evidence-based recommendations. In particular, I discuss how organisations may support positive cooperative actions through communication and rhetoric, through the adoption of human resource management practices related to selection and training, and through boundary-spanning processes and leadership roles.