Gliomas which are one of the most common types of primary brain tumors are originated from glial cells. Type of tumor and tumor location are the most important factors to determine the treatment options. The treatment options might be surgery, radiation therapy, chemotherapy, targeted therapies, and experimental clinical studies. Especially, in course of chemotherapy and radiotherapy, antioxidant levels decrease. Antioxidants fight against the oxidants' negative effects, which include cell damage, oxidative stress, and so on. Recent years, some researchers present that the antioxidant using could be harmful in some cases. A growing body of evidence suggests that antioxidant supplementation might increase the mortality. In this chapter, an overview of antioxidants and their functions has been presented to introduce researchers to the changes and effects of the antioxidants in glioma treatment. The evidence-based studies have been summarized. These experimental studies are important to understand the right option for the patient and transfer the solution from bench to bed.