The association of trigeminal neuralgia and Arnold-Chiari malformation (ACM) is uncommon. We report two cases of trigeminal neuralgia as the first and single clinical feature of an ACM. The pathophysiological relationship between ACM and trigeminal malformation is discussed. Also, the need for magnetic resonance imaging in trigeminal neuralgia is emphasized, as this is a noninvasive study which may provide valuable etiological information and prevent the progression of the disease.