Differences in knowledge backgrounds hinder the work of cross-functional teams by making knowledge integration more difficult, especially when the teams are confronted with novelties in new product development (NDP) projects. Boundary objects are attributed to a mediating capability. While design artifacts are often used to facilitate communication in design thinking (DT) projects, their significance for collaborative problem-solving in cross-functional teams is still unknown. Addressing the gap, we analyze why particular artifacts turn into boundary objects and how these boundary objects can be used in practice to facilitate problem-solving during the NPD process in DT projects. Building on the results of semi-structured interviews with representatives of five DT project teams, we illustrate the insights that boundary objects afford into the practices of stakeholder integration. Our work can help shed new light on the phenomenon, especially concerning the coordinating potential of design artifacts in DT projects. After discussing these insights, we outline directions for future research. We conclude by noting the managerial implications of our findings.