OBJECTIVE The aim of the present study was to examine and compare the long-term effectiveness of the Integrated Supported Employment (ISE) programme, which consists of individual placement and support (IPS) and work-related social skills training, with the IPS programme on the vocational and non-vocational outcomes among individuals with severe mental illness (SMI) over a period of 3 years. METHODS One hundred and eighty-nine participants with SMI were recruited from two non-government organizations and three day hospitals in Hong Kong and randomly assigned into the ISE (n = 58), IPS (n = 65) and traditional vocational rehabilitation (TVR) (n = 66) groups. Vocational and non-vocational outcomes of the ISE and IPS participants were collected by a blind and independent assessor at 7 11, 15, 21, 27, 33 and 39 months after their admission, whereas the TVR groups were assessed only up to the 15th month follow up. RESULTS After 39 months of service provision, ISE participants obtained higher employment rate (82.8% vs 61.5%) and longer job tenure (46.94 weeks vs 36.17 weeks) than the IPS participants. Only 6.1% of TVR participants were able to obtain employment before the 15th month follow up. Fewer interpersonal conflicts at the workplace were reported for the ISE participants. Advantages of the ISE participants over IPS participants on non-vocational outcomes were not conclusive. CONCLUSIONS The long-term effectiveness of the ISE programme in enhancing employment rates and job tenures among individuals with SMI was demonstrated by this randomized controlled trial.