In this study, the relationship between investment portfolio of banks and economic growth in Nigeria was examined. The work was designed to find out the structure and trend of bank investment portfolio in Nigeria and to establish the relationship between gross domestic product, unemployment rate, per capita income and bank investments in treasury bills, bonds and shares in Nigeria from 1985 to 2015. The desk research design was used and secondary data obtained from the Central Bank of Nigeria (CBN) Statistical Bulletin, publications of the National Bureau of Statistics (NBS) as well as internet sources, among others.The data collected were analyzed using the regression models and various test statistics including the tstatistic, f-ratio and Dublin Watson statistic. It is discovered that there exist significant relationship between the variables of economic growth and the variables of investment portfolio of banks in Nigeria. It was therefore concluded that although; there exist statistical significant relationship between the variables of economic growth and those of investment portfolio of banks in Nigeria, the real situation in the country is rather that of marginal and/or insignificant relationship. This is in view of the fact that even when there is an observed continuous increment in the total investment portfolio of banks, the level of economic growth in the country is rather abysmal. From the conclusions above, it was recommended, among others, that bank should restructure their investment portfolio with focus on long term securities to ensure increase in the maturity and the volume of funds made available to the borrower through such investments and the various investment portfolio adjustments by banks in reaction to monetary policy changes and interest rate movements in the country should be properly managed, timed and harnessed with the bank policies, objectives and economic growth aspiration and direction of the government