GABA is an essential neurotransmitter in tissues other than the brain and has different functions. Cancer displays dysfunctional GABAergic system roles, comprising GAD, GABA, and GABA receptors. Both tumor-suppressing and carcinogenic characteristics of the GABAergic system have been reported in several malignancies. In the development of cancer cells, it plays oncogenesis- related roles. However, in some tumors, such as pancreatic cancer, it exhibits anti-cancer benefits in numerous human trials and animal models. As a result, GABAergic therapy may be used to treat cancer. The oxidative condition and the status of several malignant circumstances significantly influence the final GABAergic function in many tumors. Depending on the type of malignant tissue and other modifications, these roles manifest differently in malignancies. In this review, we, for the first time, concentrated on the oncogenic and tumor suppressor functions of GABA in various neoplasms, as well as its potential therapeutic implications. The significance of tumor suppressor function and the conditions that promote its function as a cancer genesis factor in cancer are discussed in this article.