Small acquirers enjoy announcement period returns that are significantly higher than announcement returns for larger acquirers, but small acquirers significantly underperform after the acquisition is consummated. We investigate why the market appears to "get it wrong" at the announcement of an acquisition by a small firm. We provide evidence consistent with an initial optimistic overreaction, followed by a correction as updated information is revealed. Overreaction is clustered in small acquirers offering stock and acquiring relatively larger targets. Low post-acquisition returns and poor fundamental performance are clustered in small acquirers offering stock and diversifying.