Background: In a recent randomized trial, we were unable to confirm the previously reported high effectiveness of CCBT. Therefore, the aim of the current study was to have a closer look at usage and acceptability (i.e. expectancy, credibility, and satisfaction) of the intervention. Methods: Depressed participants (N = 200) were given login codes for Unsupported online CCBT. A track-and-trace system tracked which components were used. We used a 9-month follow-up period. Results: Uptake was sufficient, but dropout was high. Many usage indices were positively associated with short-term depressive improvement, whereas only homework was related to long-term improvement. Acceptability was good and expectancy could predict long-term. but not short-term Outcome. Limitations: Associations between use of CCBT and improvement are merely correlational. Our sample was too depressed in relation to the scope of the intervention. We relied oil online self-report measures. Analyses were exploratory in nature. Conclusions: Although CCBT might be a feasible and acceptable treatment for depression, means to improve treatment adherence are needed for moderately to severely depressed individuals.