Applying a life-span approach of human development and using the example of science-based business idea generation, the authors used structural equation modeling to test a mediation model for predicting entrepreneurial behavior in a sample of German scientists (2 measurement occasions; Time 1, N = 488). It was found that recalled early entrepreneurial competence in adolescence predicted business idea generation. This link was mediated by entrepreneurial human and social capital. Moreover, an entrepreneurial Big Five profile was associated with early entrepreneurial competence and predicted entrepreneurial human and social capital. Results underscore the relevance of the long-neglected developmental approach to entrepreneurship.