We provide new evidence on the effect of monetary policy on investment in Australia using firm-level data. We find that contractionary monetary policy makes firms less likely to invest and lowers the amount they invest if they do so. The effects are similar for young and old firms, indicating that the decline in the number of young firms in Australia over time is unlikely to have weakened the effect of monetary policy. The effects are also broadly similar for smaller and larger firms. This suggests that evidence that some, particularly large, firms have sticky hurdle rates does not mean that they do not respond to monetary policy. It also suggests that overseas findings that expansionary monetary policy lessens competition by supporting the largest firms likely do not apply to Australia. We find evidence that financially constrained firms, and sectors that are more dependent on external finance, are more responsive to monetary policy, highlighting the important role of cash flow and financing constraints in the transmission of monetary policy. Finally, we find evidence that monetary policy affects firms' actual and expected investment contemporaneously, suggesting that expectations are reactive and will tend to lag over the cycle.