This chapter examines personality development using the human agency concept as an overarching theme. It first articulates fundamental assumptions about agency, with a quick sketch of its organismic meta theoretical roots. Second, it explores the philosophical and historical underpinnings of agency as a central concept in both past and present psychological theories. It then examines the various layers of agency and discusses their development antecedents and consequences. Finally, building on the rich historical literature and recent theorizing, it concludes with some comments and suggestions on future directions.