Introduction: Addiction is a neuropsychological condition characterized by the involvement of brain reward pathways, particularly the dopamine pathway to the prefrontal cortex. Brain imaging has helped identify addiction-related changes, but it has limitations. Functional near-infrared spectroscopy (fNIRS) addresses these gaps by providing a portable and cost-effective solution. Materials and Methods: This study includes a systematic review of all articles published in Persian and English in the PubMed, Scopus, Web of Science, Science Direct, Scientific Information Database, and Noor Specialized Journal Website up to November 5, 2024. The keywords included "Functional near-infrared spectroscopy," "fNIRS," "Spectroscopy, Near-Infrared," "Substance Abuse," "Substance-Related Disorders," and "addiction," along with their Persian equivalents. Studies involving individuals with substance abuse who performed fNIRS were included. Results: The review initially included 102 articles, with findings from 23 studies analyzed. Results indicated a significant increase in fNIRS studies in recent years, with methamphetamine studies making the most use of this method. The prefrontal cortex, particularly the DLPFC, OFC, and FPA regions, was the most frequently measured area by fNIRS. The most common cognitive tasks involved craving-inducing images, whereas tasks related to working memory, attention, movement, and decision-making were used less frequently. Conclusion: This review indicates that addiction is associated with impaired executive function and disrupted reward circuits. fNIRS findings are consistent with fMRI and EEG results, emphasizing the role of the prefrontal cortex in cognitive control and craving regulation. Due to its portability and real-time data capabilities, fNIRS is a valuable tool for monitoring treatment progress and assessing the risk of relapse. However, the lack of standardized protocols and variations in experimental designs and data analysis make it difficult to compare results across studies.