Diversified firms suffer from value discount due to overinvestment and inefficient cross-subsidization. This paper conjectures that conditional conservatism ex ante reduces manager proclivity for inefficient decision, and ex post facilitates investor monitoring. This paper shows that conditional conservatism mitigates overinvestment and inefficient cross-subsidization, thereby mitigating value discount in diversified firms. The FASB issued SFAS No. 131 to improve the quality and quantity of segment information. Under SFAS No. 131, managers have less ability to offset information, and fewer incentives to make inefficient decisions. This paper shows that conditional conservatism reveals a less pronounced mitigating effect on overinvestment and inefficient cross-subsidization after implementing SFAS No. 131.