The Teamwork Knowledge, Skill, Ability Test (TWKSAT), designed to assess teamwork competencies, has been widely used in both applied and academic contexts. However, studies have brought to light a number of reliability problems in the test. In this article, we describe 3 studies that (a) examined the functioning of the TWKSAT (N = 135); (b) investigated a new measure, the Teamwork Competency Test, including its metric properties (N = 120); and (c) analyzed the convergent and predictive validity of the Teamwork Competency Test compared with the TWKSAT (N = 91). Based on our results, we conclude that the TWKSAT does not adequately reflect the initial substantive model and has limitations with regard to reliability. The Teamwork Competency Test improves the TWKSAT by enhancing reliability, content validity, and substantiating the dimensional structure of the test.