Kiloh-Nevin syndrome is one of the neuropathies where anterior interosseous nerve gets compressed by accessory head of flexor pollicis longus muscle. This study was designed to look for prevalence, morphology and relation of accessory head to anterior interosseous nerve. The present study was conducted in the Department of Anatomy, Sree Narayana Institute of Medical Sciences, and Ernakulam. 50 upper limb specimens were dissected to expose the accessory heads and its relation to anterior interosseous nerve. The number of accessory heads was noted down and length of the muscle belly was measured with vernier callipers. The accessory heads were present in 18 specimens (36%). 12 specimens with accessory head were observed to get inserted to tendon of flexor pollicis longus and 6 specimens to tendon of flexor digitorum profundus. Double accessory heads were observed in 3 specimens (6%). 3 specimens showed origin of accessory heads from flexor digitorum superficialis. Double accessory heads arising from flexor digitorum superficialis got inserted into flexor pollicis longus and flexor digitorum profundus separately. The accessory heads were related superficially to anterior interosseous nerve in all specimens. The mean length of accessory head on right side was 6.9 cms and 7.4 cms on the left side. The presence of accessory heads to flexor pollicis longus or flexor digitorum profundus acts as a trigging factor for compression of anterior interosseous nerve. The below results will give an additional information to surgeons who approach upper end of radius from anteriorly and even clinicians can plan appropriate management for compression syndromes.