Background: Surgical site hematoma is one of the factors that influence the results of the carpal tunnel release (CTR) and patients’ satisfaction; therefore, this study was designed to evaluate the effects of using Penrose drain to reduce the operation site hematoma and improve the results of surgery.
 Methods: Patients with a diagnosis of carpal tunnel syndrome (CTS) were randomly divided into intervention and control groups and then were evaluated by pain with the visual analog scale (VAS) and pinch power. The Penrose drain was placed for the intervention group and removed after two days. Three months after surgery, all patients were re-evaluated by VAS and pinch power.
 Results: Out of 46 patients, Penrose drains were placed for 21 patients. According to the results, the VAS and pinch power evaluations were better in patients with Penrose drain (P = 0.001) but in patients without Penrose drain, only the VAS evaluation results were improved, but a decrease in pinch power was detected.
 Conclusion: CTR surgery with or without the Penrose drain decreases pain in patients after three months of operation. CTR with Penrose drain improves pinch power and also decreases the pain, but in patients without Penrose drain, pinch power was reduced after this period.