Objectives The purpose of this study was to investigate clinical profile, efficacy, and safety of long-term treatment with selective serotonin reuptake inhibitors (SSRIs) in Korean autism spectrum disorders (ASDs) patients. Methods Effectiveness was assessed through a retrospective review of self-reported target symptom improvement at the last follow-up visit. Changes in illness severity and improvement were measured using the Clinical Global Impression-Severity (CGI-S) of illness and Clinical Global Impression-Improvement (CGI-I) Scales. Tolerability was assessed through a review of the reason for discontinuation of SSRI and documented adverse events. Results A total of 21 ASDs patients (aged 9 to 19 years) treated with SSRI during July 2010 to July 2011 in department of child and adolescent psychiatry of Seoul National Hospital were identified. The mean duration of SSRI treatment was 47.9 (standard deviation = 36.9) months (range 0.7-114.5), and the mean fluoxetine equivalent dosage of SSRIs was $27.1{pm}10.8$ mg. Nineteen (90.5%) patients were using concomitant medication. We found that SSRIs were prescribed for symptoms of agitation, stereotyped behavior, aggression, depression, impulsivity and self-injury in ASDs. Ten patients (47.6%) reported improvement in their target symptom after SSRI treatment based on CGI-I scores (CGI-I ${leq}$ 2). The side effects were reported in 5 patients (23.8%) ; vomiting (n = 2, 9.5%), excessive mood elevation (n = 1, 4.8%), insomnia (n = 1, 4.8%), somnolence (n = 1, 4.8%) and decreased appetite (n = 1, 4.8%). Self-injurious behavior was reported in one patient (4.8%). Conclusions The results of this study suggest that SSRIs may be used effectively in children and adolescents diagnosed with ASDs. However, safety issues need to be considered carefully when choosing SSRIs for treatment. Future controlled trials are needed to confirm these findings.