Erb's palsy or Erb-Duchenne palsy is a paralysis of the arm caused by traction injury to the upper trunk of the brachial plexus. It is commonly, but not exclusively, caused by dystocia, an abnormal or difficult childbirth or labour. It can occur if the infant's head and neck are pulled towards the side at the same time as the shoulders pass through the birth canal. Erb's palsy in adults is comparatively uncommon; it may follow trauma to the head and shoulder causing violently stretching of the nerves of the upper trunk of the brachial plexus. The anatomical basis of the clinical presentations has not been described in the literature, thus clinical diagnosis is difficult. In the current paper, case of Erb's palsy in an adult is presented. It has been demonstrated that, suprascapular nerve (C5, 6), musculocutaneous nerve (C5, 6, 7) and axillary nerve (C5, 6) are the branches of the brachial plexus involved in Erb's palsy. The skeletal muscles innervated by these nerves are severely affected compared to the cutaneous nerves that supply general sensation to the skin. The Erb's palsy in adult is very uncommon, the knowledge of this anatomy of the clinical presentation is important in the diagnosis and proper management of the condition.