During routine gross anatomical dissection of the right forearm and hand region of a 61 year old male cadaver, an unusual muscle originating from the tendon of palmaris longus muscle was observed. This muscle originated 3.1 cm proximal to the proximal end of flexor retinaculum and coursed superficial to the retinaculum to reach the hypothenar region. In the hypothenarregion, 5.2 cm distal to the proximal end of flexor retinaculum, the muscle fibers became tendinous and this tendon was inserted to the medial side of the base of fifth proximal phalanx. In this cadaver, muscle fibers of flexor digiti minimi brevis was also inserted to the medial side of this variant tendon in a unipennate manner and reached to its final insertion. Our case is unique and the possibility of the presence of such an anomalous huge muscle must always be remembered by the clinicians when a patient has findings of ulnar nerve compression syndrome or hypovascularity symptoms in the hand area due to the compression of ulnar artery.