Following the adoption of state laws that increase firing costs, there is an immediate and persistent 30% reduction in total mergers and acquisitions (M&A) dollar volume and average M&A size as well as an immediate increase in withdrawn deals. Firing costs do not affect M&A announcement returns, but there are negative returns surrounding the announcement of state laws that increase firing frictions, especially for future M&A targets. These findings suggest that post-merger employee turnover is a first-order source of value for U.S. mergers.