This paper revisits the bank competition-stability nexus in European banking from a novel angle treating jointly and interactively a set of competition and concentration measures. We explore the impact of the Lerner index, the Boone indicator, and the 5-bank concentration ratio on credit risk for a panel of 36 European countries during 1999–2019. Our findings based on system-GMM estimations provide support for a non-linear competition-stability relationship such that market power enhances banks’ credit risk in an inverse U-shaped form. We find that there is a threshold level of market power beyond which credit risk deteriorates. Our results are enhanced when an efficiency-based competition measure, the Boone measure, is interacted with the market power indicator, the Lerner index: stronger the role of efficiency in driving competitive position of banks, weaker is the impact of market power on credit risk. We also find support for a “concentration-stability” argument implying that concentration does not necessarily imply lack of competition: competition and concentration may coexist with a favorable impact on bank stability if contestability is maintained in the presence of leading banks with efficiency advantages. Policy makers should monitor a wider mix of competition-concentration measures as an additional macroprudential channel to ensure bank stability.