The diagnosis of an acquired vertical strabismus is not always straightforward. There is no one specific test that will diagnose a vertical deviation. The clinical presentation, signs, and symptoms are the driving forces that will help lead to the correct diagnosis. Patients with binocular vertical diplopia may have symptoms of recent onset or that have been long-standing. Others may not even be completely aware that their ocular symptoms are attributable to a doubled vertical image. The differential diagnosis for vertical diplopia includes oculomotor nerve palsy, superior oblique palsy, restrictive ophthalmopathies, myasthenia gravis, and skew deviation. This differential diagnosis is best used to sort out signs and symptoms in a patient with a vertical misalignment and diplopia. Because most clinicians feel more comfortable addressing the patient with complaints of horizontal diplopia, this paper will discuss the causes of vertical diplopia so that recognition will be easier, thus leading to more accurate diagnoses.