We report a case of treatment-resistant obsessive-compulsive disorder (OCD) that was successfully treated with a pharmacological augmentation of topiramate plus paroxetine. The patient, a 45-year-old woman, was on a stable dose of paroxetine (40 mg/day) when she was started on topiramate (up to 150 mg/day). After 9 weeks of this treatment, her clinical condition remarkably improved, as indicated by a significant decrease of the evaluation scales (Yale-Brown Obsessive-Compulsive Scale and Clinical Global Impression Scale). Our case suggests that topiramate might be beneficial in augmentation with selective serotonin reuptake inhibitors in patients with treatment-resistant OCD, although further investigations are warranted to confirm our findings.