PurposeThe purpose of this paper is to examine the extent of bank earnings smoothing during mandatory International Financial Reporting Standards (IFRS) adoption in Nigeria, to determine whether mandatory IFRS adoption increased or decreased income smoothing among Nigerian banks.Design/methodology/approachThe authors employ panel regression methodology to estimate the association between loan loss provisions (LLPs) and bank earnings.FindingsThe authorse find that the mandatory adoption of IFRS is associated with lower earnings smoothing among Nigerian banks, which implies that Nigerian banks do not use LLPs to smooth reported earnings during the mandatory IFRS adoption period. The authors find evidence for earnings smoothing via LLP during voluntary IFRS adoption. Earnings smoothing is not significantly associated with listed and non-listed Nigerian banks during voluntary and mandatory IFRS adoption. Overall, the findings indicate that mandatory IFRS adoption improves the informativeness and reliability of LLPs estimate by discouraging Nigerian banks from influencing LLPs for earnings smoothing purposes during the mandatory IFRS adoption. The findings of this paper are relevant to the debate on whether IFRS reporting improves the quality of financial reporting among firms in Nigeria.Practical implicationsOverall, the findings indicate that mandatory IFRS adoption improves the informativeness and reliability of LLPs estimate by discouraging Nigerian banks from influencing LLPs estimates to smooth earnings during the period of mandatory IFRS adoption.Social implicationsThe implication of the study is that IFRS has higher accounting quality than local GAAP in Nigeria as it improves the quality and informativeness of accounting numbers (LLPs and earnings) reported by Nigerian banks during the period examined.Originality/valueThis study is the first attempt to focus on income smoothing during mandatory IFRS adoption in Nigeria.