A 71-year-old male with a history of Stage IIIa squamous cell lung cancer, s/p tumor excision and treated with four cycles of docetaxel with cisplatin, presented with complaints of episodic dizziness and progressive cognitive decline, 3 months following his last dose of chemotherapy. The dizzy spells occurred due to orthostasis however, one spell was reported to be associated with headache, blurry vision, unresponsiveness followed by generalized tonic-clonic seizure that lasted for about 20 minutes. A magnetic resonance imaging (MRI) of the brain showed vasogenic edema affecting occipital and parietal lobes (left>right). He was diagnosed with posterior reversible encephalopathy syndrome (PRES) and treated with lacosamide. His memory problems included word-finding difficulty, framing false stories, and unable to follow commands. He describes his gait as “wobbly” and had difficulty coordinating movements especially on the right. Neurological examination showed difficulty to follow complex commands, right pronator drift, alien limb phenomenon in the right extremities. Repeat MRI showed significantly progressing infiltrative white matter changes within bilateral forceps major, occipital, and parietal lobes (left>right). MR spectroscopy showed findings consistent with severe demyelinating process. A brain biopsy was performed to rule out amyloid angiopathy and results were inconclusive. He had rapid clinical decline and was send to hospice care, where he developed aspiration pneumonia. He was treated symptomatically and started on steroids. After 6 weeks of treatment, there was close to complete resolution of his neurocognitive symptoms and MRI findings. Hence, we diagnosed him with delayed leukoencephalopathy secondary to chemotherapy.