The study examined the relationship between income smoothing and financial performance of firms listed on the Nigerian Stock Exchange after the adoption of IFRSs. Data for the study were quantitatively retrieved from the annual reports and accounts of the studied companies for the year 2013-2017. Pearson correlation and regression was used to analysed the data and it was revealed by fixed effect regression model that income smoothing had a positive and significant relationship with financial performance measured by ROA in Nigerian listed companies. For the control variable, corporate governance was proxed as board independence had a positive and significant relationship with firms’ financial performance in Nigeria. The study therefore recommended that financial statements’ users should be aware that managers can engage in income smoothing to manipulate the financial performance of the company and they should not base their decisions on the financial performance of the company except stronger corporate governance mechanisms are maintained.  In addition, the management should maintain optimum number of percentage of outside directors (non-executive directors) on the total board members in order to continuously maximising the best return on their investments.