The anterior muscles of the forearm consist of three layers, the superficial, intermediate, and deep flexor. All three layers are located in the flexor compartment.

Among the superficial muscles is the flexor carpi ulnaris. It arises, along with the other superficial muscles, from the medial epicondyle of the humerus. But the flexor carpi ulnaris muscle has an additional attachment point on the head of the ulna. It inserts into the pisiform bone, the hook of the hamate, and the base of the fifth metacarpal.

Blood is supplied to the muscle by the ulnar collateral arteries, the anterior and posterior ulnar recurrent arteries, and small branches from the ulnar artery. The flexor carpi ulnaris is served by the ulnar nerve (C7, C8, and T1), which enters the flexor compartment between the humeral and ulnar attachment points for the muscle.

The flexor carpi ulnaris muscle works in tandem with the extensor carpi ulnaris to flex the wrist or adduct it (move it laterally in the direction of ulnar).