A 43-year-old man was admitted for head trauma after falling backward. The patient complained of diplopia. Unilateral internuclear ophthalmoplegia (INO) was diagnosed during the neurologic examination. Initially, no specific finding was shown on T2-weighted, T1-weighted, and fluid attenuated inversion recovery brain magnetic resonance image (MRI) or brain computed tomography (CT). However, susceptibility-weighted imaging (SWI) definitively demonstrated a tiny hemorrhage at the midline of the pontomesencephalic junction. The patient's symptom improved after 12 weeks. We discuss the clinical significance of SWI when traumatic INO due to a tiny hemorrhage is suspected.