We develop an empirically grounded understanding of how design knowledge accumulates over time. Drawing from theory on knowledge creation, we conceptualize accumulation along the goals and scope of knowledge in DSR as a distinct knowledge creation problem. Through two empirical studies, we theorize knowledge accumulation in DSR by unpacking (1) three knowledge creation mechanisms, and (2) explaining how their interplay forms different patterns of knowledge creation over time. We contribute a theoretical framework conducive to integrating knowledge produced through different methods by introducing the knowledge creation processes as a distinct unit of analysis in DSR and by pointing out that extant procedural models may need revision to account for the continuous knowledge creation occurring in potentially multiyear DSR projects.