Internet-delivered CBT interventions effectively improve different aspects of mental health, although the therapists role remains unclear. The aim of this trial was to evaluate the efficacy of a therapist-supported 6-week internet-delivered intervention in improving stress recovery among healthcare workers compared to a group with optional therapist support. A total of 196 participants were recruited and randomly allocated to regular therapists support or optional therapists support groups. The primary outcome measure was the Recovery Experiences Questionnaire (REQ), developed to assess four components of stress recovery: psychological detachment, relaxation, mastery, and control. Secondary outcomes measured perceived stress (PSS-10), anxiety (GAD-7), depression (PHQ-9), and psychological well-being (WHO-5). All four stress recovery skills improved significantly after participating in the intervention at a 3-month follow-up, with small to medium effects (0.27-0.65) in both groups. At follow-up, we also found a significant reduction in perceived stress, depression, and anxiety in both groups, as well as an improvement in psychological well-being. The results indicate that ICBT can be effective in improving stress recovery skills among healthcare workers with optional support from the therapist, provided at the participants request. This RCT suggests that optional therapist support could meet participants needs and reduce resources needed in routine care.