Aftercare services are not part of the usual care for people with severe mental disorders in Iran. This study was performed to assess the cost-effectiveness of aftercare services, including telephone follow-up or home visit, in addition to caregivers' education and training of social skills, for all subjects during the 20 months after hospital discharge. An economic evaluation was performed along with a registered randomised controlled trial (IRCT201009052557N2) on two groups of 60 persons recruited between 2010 and 2012. Intervention's effectiveness was measured by psychopathology and quality of life indicators. Cost-effectiveness and cost-utility were analysed from the societal and Ministry of Health (MoH) perspectives. All indicators of psychopathology, quality of life and satisfaction with services in the intervention group were significantly different from the control group. Mean intervention costs was US$674 (95% confidence interval [CI]: 572-776) per subject in the intervention group. Average total direct costs were US$1445 (95% CI: 1086-1804) and US$1640 (95% CI: 1087-2093) per subject in the intervention and control groups respectively. From the societal perspective, intervention had more effects with lower costs. The ratios for incremental cost-effectiveness was US$8399.1 (95% CI: 8178.2-8620.0) per quality-adjusted life year (QALY) gained from the MoH perspective for 20 months of follow-up. This study showed that aftercare services can create opportunities to use hospital beds more efficiently for unmet needs of people with psychiatric disorders. Indirect and intangible costs were not considered in this study, if taken into account, they are likely to further increase the efficiency of intervention.