The present study aimed to examine whether patients' pretherapy motivation was related to other patient characteristics and whether it predicted retention in psychotherapy. Data were collected within a naturalistic outcome study of various forms of psychotherapy for patients (N = 172) with substance use disorders (SUD). Therapy motivation was measured using the Client Motivation for Therapy Scale (CMOTS), including the variables autonomous motivation, controlled motivation, and amotivation. Female patients had higher levels of autonomous motivation (d = .53), lower levels of controlled motivation (d = -.32), and lower levels of amotivation (d = -.62). Level of symptoms and impairment was significantly positively correlated with controlled motivation (r = .31). Autonomous motivation was positively correlated with four expectation subscales associated with constructive therapeutic work, whereas amotivation was negatively correlated with three of these subscales. Controlled motivation was positively correlated with the subscales external orientation, defensiveness, and support. In a logistic regression, amotivation stood out as a negative predictor of retention, in terms of starting in psychotherapy after assessment or not. Quite surprisingly, autonomous motivation was not a significant predictor of retention. The present study indicates that amotivation is a risk factor for early dropout among SUD patients. More efforts should be directed at preparing patients for psychotherapy through strengthening motivation.