Display omitted •Protocol discrepancies and spin in psychotherapy research are investigated in detail.•Discrepancies are less frequent in prospectively vs retrospectively registered trials.•Psychotherapy trial registration is not associated with less spin in the publications. This study aimed to investigate the relationship between trial registration, trial discrepancy from registered protocol, and spin in nonpharmacological trials. Recent psychotherapy trials on depression (2015–2018) were analyzed regarding their registration status and its relationship to discrepancies between registered and published primary outcomes and to spin (discrepancy between the nonsignificant finding in a study and an overly beneficial interpretation of the effect of the treatment). A total of 196 trials were identified, of which 78 (40%) had been registered prospectively and 56 (29%) had been registered retrospectively. In 102 (76%) of 134 registered trials, discrepancies between trial and protocol were present. Of 72 trials with a nonsignificant difference between treatments for the primary outcome, 68 trials (94%) showed spin. Discrepancies from protocol were less frequent in prospectively than in retrospectively registered trials (odds ratio= 0.19; 95% confidence interval CI: 0.07–0.52), but regarding the amount of spin, there was no difference between prospectively and retrospectively registered trials (rb = −0.12; 95% CI: −0.41 to 0.19) or between registered and unregistered trials (rb = −0.22, 95% CI −0.49 to 0.08). Protocol discrepancies and spin have a high prevalence in psychotherapy outcome research. The results show no relation between registration and spin, but prospective registration may prevent discrepancies from protocol.