Objectives Skin-picking disorders, trichotillomania, and nail biting are all characterized by repetitive behaviors resulting in functional deterioration and remarkable changes in physical appearance with repeated attempts to stop or decrease the behavior. While standard pharmacotherapy for obsessive-compulsive disorder and related disorders consists of serotonergic reuptake inhibitors, their moderate efficacy pushed researchers to find alternative treatment approaches. Some of these alternatives are glutamate-modulating agents. The most widely studied of these glutamate modulator agents is N-acetylcysteine (NAC), which is a derivative of the amino acid cysteine. Methods This report describes a case series of 3 patients in whom skin-picking disorders, trichotillomania, and nail biting were diagnosed at a center in Turkey. Results First case was a 42-year-old female patient who had been picking her skin from her arm area, especially in stressful times. Second case was a 31-year-old female patient who has a habit of pulling her hair for the last 20 years. The third case was 24-year-old male patient with a habit of eating his own nails that he has had for as long as he could remember. We successfully treated 3 of our patients who suffer from previously mentioned disorders with NAC. Conclusions Outcome of our cases demonstrates the efficacy of NAC, which is effective and well tolerated on the treatment of obsessive-compulsive disorder-related disorders.