Anxiety disorders, bipolar disorder, and depression are prevalent mental health issues that have a substantial impact on both individuals and the community. Many people continue to have symptoms and do not get the right kind of relief from their existing drugs, even after trying conventional therapy methods. Therefore, to enhance the current treatment modalities and patient results, new therapeutic alternatives are required. In recent years, there has been an increase in interest in N-acetylcysteine (NAC) because of its many biological benefits, including its ability to modulate glutamate levels and its antioxidant and anti-inflammatory properties. According to studies, NAC has encouraging anti-depressant properties and may help treat bipolar disease by stabilizing mood and reducing the risk of relapses. Furthermore, through lowering oxidative stress and modifying neurotransmitter networks, NAC has been shown to lessen the symptoms of anxiety. The preclinical and clinical research examining the efficacy of NAC in depression, bipolar disorders, and anxiety are thoroughly analyzed in this review.