Models of capital market imperfections predict that information asymmetry decreases firm investment and increases the sensitivity of investment expenditures to fluctuations in internal funds. Previous empirical tests of the link between investment and financing decisions have relied on indirect measures of financial constraint due to market frictions. In contrast, we use more direct measures derived from the market microstructure literature. Consistent with the theoretical predictions, our analysis shows that scaled investment expenditures are on average lower and the investment–cash flow sensitivity is greater when the probability of informed trading is high. Our results are robust to alternative measures of informed trading and liquidity, but they are not pervasive in our sample.