Using a unique hand-collected dataset from listed firms in New Zealand (2000-2020) – a country that adopts the principles-based corporate governance regime, we investigate the relationship between CEO tenure and firm performance. We document a significant positive impact of CEO tenure on firm performance, implying the benefits of long tenure. However, our study further reveals a significant inverted U-shaped relationship between CEO tenure and firm performance, suggesting that such a positive impact can hold up to a certain threshold; after that, long CEO tenure can hinder firm performance. Our finding is robust to alternative measures and endogeneity tests and offers important implications for corporate governance policies and practices.