Abstract. The study examined the efficiency of banks Nigerian using financial ratios in pre and post IFRS regime. Specifically, the study was conducted through comparison of the ratios that were computed from IFRS-financial statements based and Nigerian GAAP-based financial reports of ten (10) commercial banks quoted on the floor of the Nigerian Stock Exchange as at 2015 (before IFRS commencement and after). Three financial ratios were selected from each of the four major categories; profitability, liquidity, leverage and investment. The paired sample t-test and Mann-Whitney test were employed in testing whether significant differences exist between the pair of ratios after the normality test has been ascertained by the Jarque-Berra tests through descriptive statistics. In all, the result shows major difference between profitability, liquidity, leverage and investment ratios of the sampled firms before and after IFRS adoption at 5% level. It is was recommended that longer years in the post-IFRS adoption period are required to ascertain IFRS benefits to Nigerian firms, in relation to financial ratios.