Crossed aphasia (CA) is defined as language impairment following right-hemispheric brain lesion in right-handed person. Exact mechanism responsible for CA is ambiguous, and recently several brain lesions have been proposed to be associated with aphasia using lesion mapping method. Corpus callosum has dual bloody supply which makes it less vulnerable to infarction. Speech difficulties such as stuttering after corpus callosum infarction have been reported in the past, but aphasia is rare, which makes CA more unique. We report an extraordinary case of CA after right corpus callosum infarction. A 74-year-old female patient with a previous history of right thalamus infarction with no neurologic sequela has developed language disturbance without apraxia 1 month ago and a diffusion-weighted magnetic resonance imaging showed newly developed infarction at right corpus callosum. The aphasia quotient of the Korean version of the Western Aphasia Battery was 2.5, implying severe global aphasia. Positron emission tomography-computed tomography showed decreased metabolism in right corpus callosum and left frontal and temporal cortex, suggesting that interhemispheric diaschisis may be responsible for the CA. This is an extraordinary case report of an isolated manifestation of CA secondary to right corpus callosum infarction.