Objective: To establish whether cognitive behavioral therapy (CBT) improves the bowel symptoms, quality of life (QOL) and psychological states of irritable bowel syndrome (IBS) patients. Methods: Randomized controlled trials (RCTs) of CBT for adult patients with IBS were searched by using PubMed, Scopus and Web of Science. The standardized mean difference (SMD) with 95% confidence intervals (CIs) of the evidence-based outcome measures of the IBS bowel symptoms, QOL and psychological states at post-treatment and follow-up was calculated. Prespecified subgroup analysis was performed. Results: Eighteen RCTs satisfied our inclusion criteria. In the subgroup analyses, CBT was more effective in reducing IBS bowel symptoms, QOL and psychological states than waiting list controls at the end of the intervention and short-term follow-up. When compared with controls of basic support and medical treatment, the effect sizes were found to favor CBT for the improvement of IBS bowel symptoms at post-treatment and short-term follow-up, but CBT was not superior to controls in improving QOL and psychological states. When comparing CBT with other psychological controls, the effect sizes were almost non-significant. Conclusions: For IBS patients, CBT was superior to waiting list, basic support or medical treatment at the end of treatment but not superior to other psychological treatments. The meta-analysis might be limited by the heterogeneities and small sample sizes of the included studies.