We study the effects of financial uncertainty on investment dynamics in the U.S. using a vector autoregression with drifting parameters and stochastic volatilities. We find time-varying negative effects of financial uncertainty shocks on investment. These effects have declined in the post-WWII period but became more pronounced in the presence of the zero lower bound episode. We also find that the response of inflation to uncertainty shocks varies over time, and these shocks do not always act like aggregate demand shocks. Remarkably, the relevance of financial uncertainty shocks is found to be negligible during the Great Recession.