We report a case of left-sided horizontal gaze palsy, ipsilateral adduction weakness, and left peripheral facial weakness, all of which indicate the lesion in the left median pontine tegmentum. The enhanced MRIs revealed a discrete left median pontine tegmental lesion, involving the abducens nucleus, MLF, and facial nerve knee. This lesion spared the area of the left PPRF. Among these structures, the area of the abducens nucleus seems to be responsible for the unilateral horizontal gaze palsy. We are not aware of any previous precise neuroradiological documentation of unilateral paralysis of conjugate gaze due to a lesion of the abducens nucleus by sagittal and horizontal MRIs.