The present research used a randomized controlled design to evaluate the effects of ‘PsyFlex6,’ an online Acceptance and Commitment Training paradigm, for behavioural therapists. Twelve participants completed the six-week ACT training protocol, while another twelve waited. All participants completed measures of psychological flexibility, psychological distress, and burnout at baseline, during training, and post training, and at one and two month follow up measures for trained participants. Later, nine control group participants accepted training, as well as an additional four new participants. In total, 21 individuals completed all training and measures; results from all participants were pooled to observe any effect of the training over all time periods. As hypothesized, initial group comparisons revealed significant benefit for trained participants over controls in areas of psychological flexibility and psychological distress. Further hypotheses that burnout components (total burnout, emotional exhaustion, depersonalization and personal accomplishment) would be improved, were not supported, but trained participants did exhibit positive change for each of these dimensions. When data were pooled, significant positive changes were observed for psychological flexibility, distress, emotional exhaustion and total burnout, after training and maintained at follow up periods. Personal accomplishment and depersonalization were also improved from baseline, but not significantly so. In general, social validity data indicate that training content was well comprehended, useful, and that strategies were often used outside of training. Therefore, these findings support the use of PsyFlex6 as a training tool for improving the psychological wellbeing of behavioural therapists.