This paper aims to determine evidence about the efficiency of commercial banks under crisis periods when compared against their regular operating periods. Particularly, the Chilean and Mexican banking industries are reviewed by an innovated Data Envelopment Analysis (DEA) methodology. Conclusive evidence of an increase in efficiency for the incumbent banks under crisis periods is presented, as measured by their Return on Assets (ROA) and Return on Equity (ROE). Finally, evidence is found showing that when considering the banks that are more efficient during the whole period of analysis, their better performance is focused during the crisis periods, measured by their ROA and ROE as performance indexes. In most cases, banks that were more efficient during the previous-to-crisis period, had a lower performance during the crisis periods.