Valproic acid (VPA) is metabolized via a variety of pathways, such as N-glucuronidation, mitochondrial β-oxiation and CYP microsomal oxidation. Hence, valproic acid is more likely to cause drug-drug interaction in comparison with other drugs. Several reports indicate possible interactions between VPA and carbapenem,such as imipenem, meropenem doripenem or ertapenem. The concurrent administration of VPA and carbapenems decrease VPA plasma concentration and develop seizure is well documented. Due to its time on market, ertapenem-induced seizures are rarely reported, especially in brain tumor patients. A 75-yearold female with brain tumor history requiring continous VPA administration experienced seizure following intravenous infusion of ertapenem. In reviewing this case, we hope to bring attention to clinician who could use more caution when co-administrate VPA and ertapenem.