We examine the impact of aid and export revenue; and their volatilities on domestic private and public investment in Cameroon. Our results show that export revenue is almost three times more volatile than aid. Export has a significant positive impact on both private and public investment, while aid has a positive influence only on public investment. Both export and aid volatilities hurt both types of investment. Through the use of interaction variables, we show that export revenue can completely eliminate the impact of aid volatility on investment, but aid is unable to do same with export volatility. Reducing export volatility is more of a priority for Cameroon than aid volatility.