Despite the consensus regarding the importance of collaborative empiricism (CE) in Beck s cognitive therapy, absent are operational definitions, measures, or empirical investigations of the construct. Existing research has centered on constructs such as the working alliance and has produced inconsistent findings. It is unclear whether CE is related to treatment outcomes, or whether it mediates other cognitive change processes. This article argues that the core meaning of collaboration in CE, sharing the work, is not captured by the most frequently used construct of the therapeutic alliance in cognitive therapy research. A theory of CE, based on self-determination theory, is developed that integrates the collaborative and empirical aspects of CE and addresses the motivational aspect of the construct.