An 87-year-old man presented with a 1-week history of transient facial numbness, followed by the onset of left diplopia 1 month later. In the neurological examination, he was found to have left abducens nerve palsy. A brain MRI showed an infiltrative lesion invading the left posterior nasal cavity and pterygopalatine fossa, and extending into the left paracavernous region. The histological diagnosis was diffuse large B-cell lymphoma. We report an unusual case of diffuse large B-cell lymphoma occurring in the sinonasal tract with unilateral abducens nerve palsy presenting as an early feature.