In this case report we present a diabetic patient with isolated, pupil-sparing, incomplete inferior division third cranial nerve palsy. Laboratory tests for the evaluation of thyroid function, infection, myasthenia gravis and autoimmune diseases were normal. Cranial computed tomography, magnetic resonance imaging and magnetic resonance angiography also showed normal findings. Accordingly, diabetes related vasculopathic third nerve palsy was suggested. The ocular signs of oculomotor palsy completely disappeared 2 months later. Although this clinical entity is rarely reported, differential diagnosis with pupil-sparing third nerve palsy of other etiologies such as compression by an aneurysm or tumor still need to be investigated.