Purpose: Neurilemoma is benign tumor of the nerve sheath which arises from Schwann cells. It is usually formed along the path of a peripheral nerve but is rarely separate from normal nerve fascicles. We experienced a patient with an isolated neurilemoma localized in the palmaris longus tendon with no connection to the major nerve trunk, which was in an unusual location and has never been reported. We report our case with the review of the literature. Methods: A 23-year-old female visited our clinic with mild pain on the mass at the flexor area of the right wrist which had been present for about one year. The physical examination revealed a $1{ imes}1cm$ sized subcutaneous mass at the flexor area of the right wrist. Sonography and computed tomography showed an ovoid, superficial solid mass on the palmaris longus tendon. Upon surgical excision, a $1{ imes}0.5cm$ sized mass attached to the palmaris longus tendon was found. The tumor had no connection with the median nerve and was detached easily from the palmaris longus tendon. Results: Histological examination demonstrated the mass to be a neurilemoma, which consists of spindle shaped cells with oval elongated nuclei arranged fascicles. No sensory dysfunction or evidence of recurrence was found during the 12 months of postoperative follow-up. Conclusion: We experienced a rare case of neurilemoma attached to the palmaris longus tendon with no connection to the major nerve trunk. We wish to emphasize its unusual location through our case and hope to expand our spectrum in exploring the upper extremity mass.