This is the first study to examine the relationship between sustainability and soundness in banking as part of an integrated reporting approach. We consider 12 major European banks over the period 2006–2016. To test the relationship, two indexes were constructed, the sustainable performance index, which attempts to measure sustainability, and the banking soundness index, which measures bank soundness. The results show a bidirectional causality between sustainability and banking soundness. More specifically, soundness encourages banks to engage in sustainable development activities, while (...) the implementation of a sustainable development approach has a negative effect on banking soundness. Our research contributes to the literature on this topic in two ways. First, we propose a new method for measuring banking soundness based on a Bayesian approach. This approach allows us to study a large number of criteria and allows us to determine proactively the importance and the contribution of different determinants in achieving soundness. In addition, to the best of our knowledge, this is the first study that attempts to study the relationship between bank soundness and sustainability. (shrink)