This study investigates whether the market can detect the productivity changes in US bank acquirers during the deregulation of the 1990s and the regulation in the aftermath of the 2008 financial crisis. We find that the market reacts negatively to acquisitions that resulted in productivity decline -especially for medium acquirers- but they show no market reaction to acquisitions that resulted in productivity increase. Moreover, the market reflects the characteristics of the deals, like a target's relative size, profitability, and percentage of short-term stock financing, while it reacts to the possible changes in productivity over longer horizons. These results apply to the deregulation and regulation periods but with longer delays in the market reactions to productivity changes and more persistence in the characteristics of deals across all event windows in the deregulation period. The practical implication for acquirer banks’ is that, besides analyzing acquisition characteristics (such as the target’s profitability, relative size, and leverage), its management has to monitor the bank’s productivity and take actions on any productivity decline.