ObjectivesTo 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.DesignPragmatic cluster randomised controlled trial, randomisation at PCC level.Setting28 PCCs in Region Västra Götaland, Sweden, with care manager organisation.Participants30 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).InterventionComplex 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 measures12 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).ResultsNo 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.ConclusionsIt 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 numberNCT03250026.