Information on the use of N-acetylcysteine (NAC) in neuropsychiatric disorders has increased in recent publications. Although there are positive reports on the use of NAC in obsessive-compulsive and related disorders (OCRD), such data have not yet been validated. This article aims to review the research, case series and case reports that have been published about the use of NAC in OCRD. Research papers and case reports on the use of NAC in OCRD published within the last five years have been reviewed using the search engines of "Pubmed" and "Medline Central" databases. The search was performed by matching the terms "obsessive-compulsive disorder (OCD)", "trichotillomania (TTM)", "nail biting", "skin picking", "hoarding disorder", and "body dysmorphic disorder" with "N-acetylcysteine". The search identified 4 papers on TTM, 3 papers on nail biting behavior, 1 paper on OCD and 1 paper on skin-picking behavior. Three of these papers were double-blind, placebo-controlled studies and four were case reports/series. The results of 2 papers out of the 7 that we reviewed showed that there was no difference between NAC and placebo, while 5 papers reported that the response to the NAC therapy was positive. We did not find any papers on the use of NAC in either hoarding disorder or body dysmorphic disorder. NAC is thought to be a promising psychopharmacologic agent in OCD, which is defined under OCRD due to its common etiology, similar clinical features and similar response to treatment, as well as in TTM, skin picking and nail biting. The effectiveness of glutamatergic modulators on repetitive behaviors or OCD has increased interest in NAC. Although there are a few studies in the area, many research projects are being planned, with some already in progress (www.clinicaltrials.gov), a fact that emphasizes the importance of NAC in OCRD treatment. NAC has been used in a broad spectrum of conditions such as paracetamol intoxication, doxorubicin cardiotoxicity, ischemia-reperfusion-induced injury of the myocardium, acute respiratory distress syndrome, bronchitis, chemotherapy intoxication and heavy metal intoxication. In recent years, there has been an increase in the number of studies exploring the use of NAC in neuropsychiatric disorders such as schizophrenia, autism, bipolar disorder and OCRD. In this review, we have seen that the results of studies assessing the efficacy of NAC in psychiatric disorders are promising; however, there is a need for further studies to evaluate its mechanism of action, appropriate dose range and duration of treatment.