The current study investigates the relationship between Organizational Identification and Organizational Citizenship Behaviour (e.g. helping colleagues, making innovative suggestions). We replicate earlier findings of such a relationship between those behaviours and organizational identification using ten samples across different occupational groups and countries in Study 1. Study 2 investigates the relationship in a longitudinal approach. Study 3 looks into this relationship on a group-level analysis while Study 4 extends our findings by linking identification to customer perceptions and financial performance, mediated by OCBs (Organizational Citizenship Behaviours).