Posterior reversible encephalopathy Syndrome (PRES) is a rare syndrome that is reversible in most cases but can rarely lead to irreversible brain damage and death. Most cases occur after rapid rise in blood pressure. We report a 56 year-old Caucasian male with metastatic adenocarcinoma of the lung who presented with a pleural effusion for which thoracocentesis and thoracotomy were performed. He developed PRES on the third post-operative day following relatively moderate increase in blood pressure. It was diagnosed with diffuse weighted imaging (DWI) MRI. He eventually fully recovered from the event. PRES is a reversible syndrome, in most cases, that can be diagnosed with appropriate imaging studies such as MRI with DWI. This case report is of clinical importance to surgeons as well as neurologists. We speculate that post surgical patients are more prone to developing PRES at lower blood pressures than blood pressures required in healthy individuals to develop PRES. Patients' post surgical blood pressure should be monitored closely and maintained at lower levels to prevent PRES. It is essential to control and diagnose PRES at an early stage since it can be easily prevented and some cases proceed to irreversible damage. It should also be differentiated from an acute cerebrovascular event since its treatment and prognosis are markedly different from PRES.