This paper suggests that in order to understand relations between different aspects of organizational learning, an appropriate unit of analysis and a concrete, historical approach is needed. The units of analysis used in representative theories of organizational learning are first reviewed and evaluated. ''Activity system'', a concept that is based on Cultural Historical Activity Theory, is then introduced as a potential candidate for a unit of analysis that makes it possible to analyze the specific historical, local challenges and problems of organizational learning and to direct a collective learning process. A case of organizational learning is then presented by using a model of the activity system and Activity Theory-based intervention methodology. Theoretical implications of the case are pointed out in discussion.