Market uncertainty has a significant impact on market participants’ decision making. This study analyzes the effect of market uncertainty on the accounting policy of firms and the asymmetric decision making behavior of investors to good and bad news. Specifically, we examine whether market uncertainty affects firm’s conservative accounting practices, and analyze how conditional conservatism affects investors’ risk-averse investment behavior. The result of this paper shows that firms are more conservative when market uncertainty increases. Firms use conservative accounting as a means to reduce the risk of market uncertainty. Consistent with prior literature, investors in Korean market also make asymmetric decisions that respond more sensitively to bad news when market uncertainty increases. However, the analysis shows that conservative accounting mitigates the asymmetric investor decision making behavior. It implies that investors perceive conservative accounting as a reasonable way to protect their investment decision making. This study has contributions that it analyzes empirically the effects of market uncertainty on the corporate accounting policies and on the investor decision making. In particular, it supports the argument that conservative accounting plays a positive role in the usefulness of accounting information. It also shows that the volatility index, VKOSPI, can be used as a measure of direct and continuous market uncertainty in Korean capital markets.