Gemcitabine is a commonly used chemotherapeutic agent for a variety of tumors. Although this nucleoside analog antineoplastic agent is similar in structure to cytarabine, central nervous system toxicities have rarely been attributed to gemcitabine. The posterior reversible encephalopathy syndrome (PRES) is a condition characterized by reversible neurological and radiological findings that has been associated with use of chemotherapeutic and more recently novel targeted therapies. We describe one case of a 41-year-old woman with PRES under treatment for leiomyosarcoma because of the probable association with gemcitabine. Our case, to our knowledge, represents the seventh published report of this particular toxicity. Naranjo algorithm, efficacious method for assessing the causality of adverse drug reactions (ADRs) from a case report, suggests a direct casual relationship. PRES is probably a rare complication of gemcitabine, but the oncologist should take it into careful consideration, because PRES is reversible with treatment of current hypertension or removal of the causative agent. However, failure to quickly recognize the syndrome and discontinue the offending agent may result in profound and permanent central nervous system dysfunction or death.