This study aims to determine the effect of macroeconomic variables on Islamic banking in OIC (Organization of Islamic Cooperation) countries. This study uses secondary data in the form of annual panel data from 2005 to 2020. The macroeconomic variables of this study are represented by interest rate (SK), gross domestic product per capita (GDPC), money supply (JUB), inflation (INF), and the exchange rate (KRS). Meanwhile, Islamic banking is represented by the total asset (TA) variable. By using the Panel Vector Error Correction Model (PVECM) data analysis method, this study showed several results, namely; The interest rate variable (SK) has an effect in the long term and short term on the total assets of Islamic banks. The variable amount of money in circulation (JUB) has an effect in the long term and short term on the total assets of Islamic banks. The variable GDP per capita (GDPC) has an effect in the long and short term on the total assets of Islamic banks. Inflation variable (INF) has an effect in the long term and does not affect the total assets of Islamic banks in the short term. The implication of the research is there are efforts from each party to reaffirm the interest rates should not be used as a reference in the application of nisbah in Islamic banks, seeking the best services so that Islamic banks are able to outperform conventional banks.