Organizational scholars have studied learning processes within and across organizational boundaries. In this paper, we introduce the concept of extra-organizational learning to explain the mechanisms that enable learning among external individuals who are not bound to the focal organization by an employment contract and yet their tasks benefit the focal organization. We study the crowdsourcing project Transcribe Bentham, where the crowd transcribes documents of historical importance, and show how participants learn by doing and by socially interacting with experts from the organization. We explain how this process of extra-organizational learning differs from known processes of inter-organizational learning and crowdsourcing as ‘distant search’ and we discuss implications for the organizational learning literature