This study investigates the emergence and the performance effects of an age-diversity climate at the organizational level of analysis. Building upon Kopelman and colleagues’ (Kopelman, Brief, & Guzzo, 1990) climate model of firm productivity as well as Cox's (1994) interactional model of cultural diversity, we hypothesize a positive influence of age-inclusive HR practices on the development of an organization-wide age-diversity climate, which in turn should be directly related to collective perceptions of social exchange and indirectly to firm performance and employees’ collective turnover intentions. The assumed relationships are tested in a sample of 93 German small and medium-sized companies with 14,260 employees participating. To circumvent common source problems, information for the various constructs was gathered from 6 different sources. To test our assumed relationships, we applied structural equation modeling and executed bootstrapping procedures to test the significance of the indirect effects. We received support for all assumed relationships. The paper concludes with practical recommendations on how to establish and make use of a positive age-diversity climate.