This paper estimates the equilibrium real effective exchange rate and determine the level of exchange rate misalignment in Sierra Leone, for the period 1980 to 2018. The paper utilizes the behavioral equilibrium exchange rate methodology within the Johansen maximum likelihood framework to estimate the long run equilibrium real effective exchange rate. The unit root test result shows that all the variables are integrated of order one, whilst the cointegration test establishes the existence of one cointegrating vector as evidenced by both the Trace and Maximum Eigen Statistics. The normalized long run results reveal that openness, government expenditure and money supply were the most significant determinants of the real effective exchange rate in the long run. Furthermore, the findings reveal that the real effective exchange rate experienced sustained deviation from the long run equilibrium real effective exchange rate during the study period, with episodes of overvaluation and undervaluation. Specifically, the real effective exchange rate was overvalued by 3.69 percent during the period between 1980-1985; undervalued by 1.8 percent between 1986-1997, and overvalued by 0.9 percent between 1998-2004, Thus, the paper reveals episodes of misalignment of the real effective exchange rate. Based on these findings, the study recommends that, the monetary authorities should ensure stability of the exchange rate and maintain price stability, through sterilization of capital flows as well as contain money growth within the statutory limit.