The highly unstable economic conditions in Nigeria desire government intervention through regulated public policies. Based on the above, the study investigated the impact of monetary policy on corporate investment in Nigeria, and seeks to examine the effect of monetary policy (interest rate) on corporate investment. Four hypotheses were formulated and tested using multiple regression technique. Data were obtained from Central Bank of Nigeria (CBN) Statistical Bulletin and Companies Annual Reports and Accounts. The Study revealed that there is no significant relationship between the volume of investment and interest rate, and there exist a weak relationship between the cost of capital and interest rate. The capital structure of firms in Nigeria is highly influence by interest rate. The ineffectiveness of interest rate has been attributed to the imperfect market conditions. Therefore, the study recommended that, the government should make an effective policy that will correct these market conditions, and interest rate policy should he applied in conjunction with other tools of public policy