Traumatic dislocation of the radial head without fracture of the olecranon is very rare, especially in adults. We experienced a case of irreducible radial head dislocation with fracture without involvement of ulna. Open reduction and internal fixation was performed. During surgery, brachialis was interposed between capitellum and radial head, and also interposed between the fragments at the fracture site of the radial head. At 12 months after operation, the radial head was well reduced with normal rotation.