Using Difference-in-Differences method and data from 5115 banks located in 74 countries over2009-2018, we investigate the effects of a negative interest rate policy (NIRP) on banks’ customerdeposit rate. Our results highlight that in response to the introduction of NIRP, banks reducedtheir customer deposit rate. We also show that this effect varies from country to country, espe-cially among eurozone countries. Finally, we find that the reduction in customer deposit rate isnot immediate and that it becomes stronger as NIRP persists over time. Overall, our findingsconfirm that banks are reluctant to reduce customer deposit rate. However, this reluctance de-creases as negative interest rates are prolonged over time.