This study examines the role of financial reporting conservatism in mitigating underinvestment problems. Recognizing that volatile cash flows increase the need to access external capital markets and that agency conflicts and information asymmetry make external capital costlier than internal capital, which leads managers to forgo valuable investment projects, Minton and Schrand document a negative relation between cash flow volatility and investment. We draw on Minton and Schrand’s framework to isolate underinvestment problems and hypothesize and document that conservatism mitigates the negative relation between cash flow volatility and investment and that this mitigative effect is more pronounced for firms with ex ante more severe agency conflicts. We also document that conservatism mitigates the sensitivity of investment to cash flow volatility by facilitating access to external capital.