The global trend of increasing workplace age diversity has led to growing research attention to the organizational consequences of age-diverse workforces. Prior research has primarily focused on the statistical relationship between age diversity and organizational performance without empirically probing potential mechanisms underlying this relationship. Adopting an intellectual capital perspective, we posit that age diversity affects organizational performance via human and social capital. Furthermore, we examine workplace functional diversity and age-inclusive management as two contingent factors shaping the effects of age diversity on human and social capital. Our hypotheses were tested with a large manager-report workplace survey data from the Society for Human Resource Management (N = 3,888). Results indicate that age diversity was positively associated with organizational performance through the mediation of increased human and social capital. In addition, functional diversity and age-inclusive management amplified the positive effects of age diversity on human and social capital. Our research sheds light on how age-diverse workforces may create value through cultivating knowledge-based organizational resources (i.e., human and social capital). (PsycInfo Database Record (c) 2021 APA, all rights reserved).