RATIONALE: Perineural cysts in the spinal canal are usually asymptomatic. However, symptoms can occur when the cyst becomes large enough to compress a nerve root. There are still no established treatment options for this disease. In this report, we describe a case of successful decompression of the large symptomatic perineural cyst using epiduroscope. PATIENT CONCERNS: A 42-year-old male patient visited our pain center complaining of discomfort and pain in his right posterior thigh. Magnetic resonance imaging of the patient showed a large perineural cyst (53 × 31 × 21 mm) compressing the right S1 nerve. No other abnormalities that would explain the patient's symptoms were identified. DIAGNOSIS: Perineural cyst at the right S1 nerve. INTERVENTIONS: We performed an epiduroscopic decompression of the perineural cyst. After advancing the epiduroscope and locating the cyst, we used the laser to make a hole in the cyst wall. Then, the epiduroscope was advanced into the cyst, and the cystic fluid was aspirated. OUTCOMES: The symptoms of the patient were relieved after the procedure, without any complications. There was no recurrence of symptoms until 6 months after the procedure. LESSONS: The epiduroscope is a minimally invasive method which can be used safely for decompression of symptomatic perineural cysts in the spinal canal.