Purpose Success in projects requires understanding and managing increasing complexity. This study aims to address the gap in the literature regarding the relationship between project complexity and various forms of interpartner learning capability. In addition, the authors explore the moderating effect of supplier design responsibility on the relationship between project complexity and interpartner learning capability. Design/methodology/approach From an electronics supplier’s perspective, the authors propose that the effect of project complexity is a process of knowledge acquisition and sharing that is facilitated by various forms of interpartner learning capability, including absorptive learning and joint learning, with the upshot of fostering name-brand customer dependence in international exchange relationships. A questionnaire survey is used to collect data from project, product and account managers in the electronics manufacturing industry. The conceptual model is tested using 226 returned questionnaires. Findings The results indicate that complex projects can drive absorptive learning and joint learning capability, fostering enhanced customer dependence and relationship performance. Further, supplier design responsibility has a positive moderating effect on the relationship between project complexity and joint learning capability. However, project complexity is not significantly moderated by the effect of supplier design responsibility on absorptive learning capability. Originality/value Complexity fosters behaviors that influence interpartner learning, which highlights the connection between project management complexity and organizational learning in theory and practice.