This study examines learning effects (i.e., the effects of prior experience) in information systems development (ISD). ISD is characterized by disparate tasks, teams, and levels of project complexity across projects. These features challenge our understanding of how learning effects occur in the ISD context. Drawing on the theory of transfer of learning, this study examines how ISD project teams learn and under what conditions the learning effects are stronger or weaker. We find that ISD project teams' experience in prior projects translates into performance gains for the current ISD project when the prior and current projects share the same domain, technology, or customer knowledge elements-domain, technology, and customer being the most essential knowledge types for ISD. Moreover, we find that the learning effects of domain, technology, and customer knowledge are substitutive for one another and that these learning effects become stronger or weaker depending on the extent of ISD projects' team and task complexities. The study makes significant contributions to the ISD literature on learning effects and the roles of domain, technology, customer knowledge, and project complexity, as well as to the general organizational learning literature. It also provides important managerial insights into practical concerns such as project staffing and knowledge acquisition for ISD organizations.