In daily life, we sometimes select temporal cues of one sort while suppressing others. This study investigated the mechanism of suppression by examining a split-brain patient’s perception of target intervals while ignoring distractor intervals. A patient with agenesis of corpus callosum and five age- and sex-matched control subjects participated in reproduction of target intervals while ignoring distractors displayed in the visual field either ipsilateral or contralateral to target. In the patient, the distractor interfered with reproduction performance more strongly when contralateral rather than ipsilateral. Our results suggest that the corpus callosum plays an inhibitory role in interhemispheric interference and that temporal interval information can be transferred via subcortical structures when there are no direct interhemispheric pathways.