By comparing firms that used to transact with merged banks with those that did not we measure the impact of financial institution mergers on firm financing in two ways. We first take a close look at a megabank merger. We then conduct a comprehensive examination of how recent financial institution mergers have affected the financing environment of firms. The key results are as follows. First, the 2006 merger between two megabanks, the Bank of Tokyo-Mitsubishi and the UFJ Bank, led to a substantial increase in interest rates among non-listed borrower firms and a decline in their loan ratios. Second, looking at the effects of financial institution mergers since 2004 we find that the financial environment for firms that transacted with merged banks has improved on average, which is the opposite of the findings for the megabank merger. Among all bank mergers since 2004 the finding of higher interest rates is unique to the megabank merger. Mergers in the 2010s resulted in a larger increase in the loan ratio for firms that previously transacted with the merged banks than for firms that did not.