Mycotoxins are secondary metabolites produced by various kinds of fungi that can induce disease in humans. The fungal species Penicillium expansum produces patulin (C7H6O4), a polyketide lactone mycotoxin found in fruits. Patulin is classified as noncarcinogen; however, recently, it has been associated with harmful effects on the central nervous system. Patulin's toxic action has been established in various brain models; however, its effect on human glioblastoma remains elusive. This study explores whether patulin induces cytotoxicity through oxidative stress in DBTRG-05MG human glioblastoma cells. This study also evaluates whether the antioxidant N-acetylcysteine (NAC) protects against patulin-induced cytotoxicity. In DBTRG-05MG cells, patulin concentration (10–60 μM) dependently induced cytotoxicity. Concerning oxidative stress, patulin (10 and 20 μM) increased the production of intracellular reactive oxygen species (ROS) but depleted reduced glutathione (GSH) contents and regulated the expressions of antioxidant-related proteins (Nrf2 and HO-1). Furthermore, patulin induced cytotoxicity via modulation of apoptosis-related protein expressions (Bax, cleaved caspase-9, and cleaved caspase-3). These cytotoxic responses were partially reversed via pretreatment with NAC (10 μM). In summary, these data help us understand the toxicology of patulin in human glioblastoma and evaluate whether NAC could clinically reduce patulin-affected brain damage.