The hallmark of service—value co-creation—is not easy to achieve in B2B IT service engagements. Typically, client and provider are both complicated organizational entities with multiple agendas and diverse stakeholders, and engagements often extend over years. We analyzed a number of IT service engagements to better understand their complex dynamics, with the ultimate goal of improving their outcomes. This paper reports on our study of how value co-creation unfolds over time, and identifies basic dynamics central to the modeling of service systems—actualization of service and realization of value—that are reflected in the proposed framework.