This paper analyses the effects on unconditional conservatism of the mandatory adoption of International Financial Reporting Standards (IFRS) by Spanish listed companies in January 2005. The lack of robustness in the previous evidence justifies analysing this issue from different perspectives. To this end, we use, for the first time in this context, Ahmed and Duellman’s methodology (J. Account. Econ., 2007). In its design, these authors consider the impact of growth options and other future incomes, controlling for the idiosyncratic factors that the literature has found to condition this type of conservatism. Additionally, beyond the pooled regression techniques usually used, we use econometric panel data techniques, which minimize the possible effect of endogeneity in the estimation of the proposed models. The results provide new evidence that supports our hypothesis that the adoption of IFRS has reduced the unconditional conservatism of Spanish listed companies.