OBJECTIVE: In the current study a brief review is presented of the coracobrachialis muscle's morphological variability, action, embryological development and clinical significance.CASE REPORT: We report a case of a left-sided coracobrachialis muscle consisting of two bellies. The deep belly inserts into the usual site in the middle area of the anteromedial aspect of the left humerus, whereas the superficial belly inserts through a muscular slip into the brachial fascia and the medial intermuscular septum, forming a musculo-aponeurotic tunnel in the middle region of the left arm, for the passage of the median nerve, brachial artery and veins, medial antebrachial cutaneous nerve and ulnar nerve.CONCLUSION: Awareness of such a muscle variant should be kept in mind by physicians and surgeons during interpretation of neural and vascular disorders of the upper limb, since such a variant may potentially lead to entrapment neuropathy and/or vascular compression, predisposing to neurovascular disorders, as well as during preparation of that muscle in cases of utilizing it as a graft in reconstruction of defects.