OBJECTIVES: To study whether early and enhanced cooperation within the primary care centres (PCC) combined with workplace cooperation via a person-centred employer dialogue meeting can reduce days on sick leave compared with usual care manager contact for patients on sick leave because of common mental disorders (CMD). Secondary aim: to study lapse of CMD symptoms, perceived Work Ability Index (WAI) and quality of life (QoL) during 12 months. DESIGN: Pragmatic cluster randomised controlled trial, randomisation at PCC level. SETTING: 28 PCCs in Region Västra Götaland, Sweden, with care manager organisation. PARTICIPANTS: 30 PCCs were invited, 28 (93%) accepted invitation (14 intervention, 14 control) and recruited 341 patients newly sick-listed because of CMD (n=185 at intervention, n=156 at control PCCs). INTERVENTION: Complex intervention consisting of (1) early cooperation among general practitioner (GP), care manager and a rehabilitation coordinator, plus (2) a person-centred dialogue meeting between patient and employer within 3 months. CONTROL GROUP: regular contact with care manager. MAIN OUTCOME MEASURES: 12 months net and gross number of sick leave days at group level. SECONDARY OUTCOMES: 12 months depression, anxiety, stress symptoms, perceived WAI and QoL (EuroQoL-5 Dimensional, EQ-5D). RESULTS: No significant differences were found between intervention and control groups concerning days of sick leave (intervention net days of sick leave mean 102.48 (SE 13.76) vs control 96.29 (SE 12.38) p=0.73), return to work (HR 0.881, 95% CI 0.688 to 1.128), or CMD symptoms, WAI or EQ-5D after 12 months. CONCLUSIONS: It is not possible to speed up CMD patients' return to work or to reduce sick leave time by early and enhanced coordination among GP, care manager and a rehabilitation coordinator, combined with early workplace contact over and above what 'usual' care manager contact during 3 months provides. TRIAL REGISTRATION NUMBER: NCT03250026.