Interdisciplinary project teams have become ubiquitous for the solution of complex research questions and the development of innovative products in both academic and industrial settings. However, the often considerable functional heterogeneity of these teams puts high demands on team members and can hinder or even endanger the accomplishment of team goals. Especially, the integration of highly specialized areas of expertise is problematic. The present paper describes the development and validation of an instrument to assess knowledge integration problems in interdisciplinary project teams in order to diagnose common barriers in interdisciplinary collaborations. The development of the scale was based on qualitative interviews with members of interdisciplinary project teams. A first validation of the scale through five independent studies ( N = 290) confirmed its validity and reliability.