Obsessive-compulsive disorder (OCD) is a prevalent mental disorder characterized by intrusive thoughts (obsessions) and ensuing rituals (compulsions). Although OC patients exhibit various cognitive and behavioral problems, rigid and hypersensitive moral judgments are known to be one of the most striking problems in these patients. There is evidence indicating that OC patients often tend to make deontological judgments in moral dilemmas, significantly more than the healthy population. Therefore, numerous studies are dedicated to understanding the underlying cognitive processes responsible for such variation of moral judgments in OCD, which are reviewed and discussed in the current paper. First, it is previously discussed that abnormal moral judgments in OCD are due to executive dysfunctions. These dysfunctions include impaired cognitive control resulting in the domination of strong, uncontrolled emotional responses, impaired cognitive flexibility resulting in the inability to switch between aspects of a scenario, and decreased capacity and overload of working memory and its inability to resist the interfering information. The dual-process theory also emphasizes and acknowledges the role of executive functions in moral judgments. Second, it is thought that disobeying moral norms results in the abnormal feeling of deontological guilt in OC patients, to which these patients are highly sensitive. Feeling of guilt is also thought to be correlated with OCD symptomatology. The third impairment contributing to abnormal moral judgments in OCD is known to be the abnormal feeling of disgust for moral violations and immoral unwanted intrusive thoughts, which is regarded as one of the major causes of OCD symptoms. Finally, the abnormal fear of responsibility and being criticized due to not acting morally is regarded as one of the primary impairments contributing to the abnormal moral judgments in OCD. In conclusion, this review sheds light on the most striking cognitive and affective impairments contributing to abnormal moral judgments in OCD.