Optic nerve aplasia is a rare congenital anomaly consisting of complete absence of the optic disc and nerve, ganglion cells and nerve fibers, and retinal blood vessels. Optic nerve aplasia may be associated or not with anomalies of the eye ball, and may be unilateral or more rarely bilateral, the latter sometimes associated with major central nervous system anomalies. We report the MRI appearance of a case of unilateral optic nerve aplasia associated with microphthalmos. Coronal T2 weighted and 3D T1 weighted images disclosed the absence of the 3 portions of the optic nerve. This observation shows the usefulness of systematic MRI in case of microphthalmos associated with suggestive anomalies of the fundus.