We study whether borrowers' opaque practices, such as tax aggressiveness, are affected by their lenders' engagement in mergers and acquisitions (M&As). Our findings suggest that borrowers' tax aggressiveness is negatively associated with bank mergers as banks increasingly rely on hard information in monitoring and lending practices following mergers. This relationship is more pronounced for borrowers that are more opaque in their information environments and have a greater need for credit, and when banks that have a greater intention to monitor borrowers and rely more on soft-information-based monitoring prior to the mergers. Our study contributes to the growing literature on whether and how bank consolidations affect borrowers' decision making.