We explore the source of managerial hubris in mergers and acquisitions by examining the history of deals made by individual acquirers. We find that compared to their first deals, acquirers of second and higher-order deals experience significantly more negative announcement effects. We also find that while acquisition likelihood increases in the performance associated with previous acquisitions, previous positive performance does not curb the negative wealth effects associated with future deals. We interpret these results as consistent with self-attribution bias leading to overconfidence. We also find evidence that the market anticipates future deals based on an acquirer's acquisition history and impounds such anticipation into stock prices.