In this study, we investigate the effects of macroprudential policies on banks’ net interest margins (NIMs) using 3000 banks in 28 European Union countries from 1996 to 2019. Macroprudential tightening results in an immediate 2 basis point (bp) decrease in the NIMs, an increase in interest income (IIEA) of 7 bp, and an increase in interest expense (IEEA) of almost 10 bp. But the last two decline by 10.5 and 10.1 bp respectively 1–2 years later. The effect depends on the instrument type and varies based on the capital ratio and credit risk, but holds in high- and low-rate environments.