We identify the effect of financial integration on international business cycle synchronization, by utilizing a confidential database on banks’ bilateral exposure and employing a country-pair panel instrumental variables approach. Countries that become more integrated over time have less synchronized growth patterns, conditional on global shocks and country-pair factors. To account for reverse causality and measurement error, we exploit variation in the transposition dates of financial legislation. We find that increases in financial integration stemming from regulatory harmonization policies are followed by more divergent cycles. Our results contrast with those of the previous studies which suffer from the standard identification problems.