Based on the theory of financial intermediation from both the perspective of original theory and the Islamicperspective, this paper aims to investigate the level of stability of the Islamic and the conventional banks. It alsoexamines the different timing effects including the period of crisis on the stability of the Islamic and the conventionalbanks. The study evaluates 51 conventional banks and 50 Islamic banks in selected Gulf Cooperation Council (GCC)using data from the Bankscope database over the period of 1999 to 2015. The study employs two-sample t-test withunequal variance t-test and the non-parametric Wilcoxon test and Mann-Whitney test to compare i) mean of Islamicversus conventional banks over different timing period ii) mean of tested period versus other periods for each of theIslamic and conventional banks. The study suggests that the GCC Islamic banks are more stable compared to theirconventional counterparts. However, in testing different timing period, only GCC conventional banks seem to beaffected by the crisis period while Islamic banks are less prone to the crisis.. Findings of this study contribute to theliterature and fill the gap towards extending the theory of financial intermediation through empirical works ofinvestigating the stability of the Islamic and the conventional banks.