Group cohesion is one factor that is widely suggested to be important in producing clinically meaningful change in group psychotherapy. However, the construct has proved difficult to define, and in an effort to capture the construct's multidimensionality, contemporary measures have become long, cognitively demanding, and challenging for people with limited literacy. In response to this, we test a single-item visual analogue scale that provides a simple, intuitive, time-efficient, and user-friendly proxy for the cohesion construct. The Group Entitativity Measure–Group Psychotherapy (GEM-GP) was validated in a clinical sample of individuals who completed a group cognitive–behavioral therapy course for depression. GEM-GP scores correlated highly with a lengthier, traditional measure of group cohesion and were just as predictive of outcomes as a multi-item, traditional measure. The GEM-GP is a valid, user-friendly, and brief proxy for the cohesion construct in the group psychotherapy context.