This paper provides a theoretical explanation for the observation that firms with strong corporate governance exhibit more conservative accounting. We study one of a board’s most important decisions: to retain or replace the incumbent manager. The board uses accounting information and additional information from costly board monitoring. We show that if the accounting information is useful only for the replacement decision, then conservatism is harmful because it leads to too much replacement. If accounting information is relevant for the board’s decision whether to monitor, then conservatism is beneficial when the board is a sufficiently efficient monitor. We also provide several predictions for empirical tests.