Background: The aim of the research was to examine whether a role-focused self-help course intervention would decrease caregiver stress and distress, and functioning problems, among people who suffer stress because they combine paid work with informal care.; Methods: A pre-registered (NTR 5528) randomized controlled design was applied (intervention vs. wait list control). Participants (n = 128) were people who had paid work and were suffering stress due to their involvement in informal care activities. Participants allocated to the intervention group (n = 65) received the role-focused self-help course. Control group members (n = 63) received this intervention after all measurements. Prior to the random allocation (pre-test), and 1 month (post-test 1) and 2 months (post-test 2) after allocation, all participants completed a questionnaire that measured their caregiver stress (primary outcome), distress, work functioning, negative care-to-work interference and negative care-to-social and personal life interference. Mixed model ANOVAs were used to test the effectiveness of the intervention.; Results: Two months after allocation, the intervention group participants had lower levels of caregiver stress and distress compared with the control group participants. The intervention did not directly resolve impaired work functioning or interference of care with work and social/personal life.; Conclusion: The intervention decreases caregiver stress and distress in people who suffer stress because they combine paid work with informal caring. The intervention (Dutch version) can be downloaded at no cost from www.amc.nl/mantelzorgstress.