Income smoothing as an accounting technique is an earnings management method that has recently piqued the interest of company boards of directors, accountants, and accounting researchers. Income smoothing is the application of financial reporting principles and standards to level out earnings volatility. This paper focussed on the theoretical investigation of the impact of the International Financial Reporting Standard on corporate governance and income smoothing. This study theoretically examined the link between board size and income smoothing, with an emphasis on the intervening effect of International Financial Reporting Standards (IFRS). This paper covers a period of 2003 to 2023 and which focussed on the Nigerian Financial Market. In this study, a systematic literature review (SLR) was performed, and the research revealed crucial impact of the International Financial Reporting Standard on corporate governance and income smoothing. The SLR was performed using a sample of 100 research articles chosen from a pool of 400 papers obtained from Scopus, Web of Science, Google Scholar, ABS journal and, among other sources. Following the findings of the many research evaluated, the study discovered significant divergence and inconsistency in the results, indicating that corporate governance has either a positive or negative association with income smoothing.