We analyze the determinants of the overnight spread (the spread between the Borsa Istanbul overnight repo interest rate and the average funding rate of the Central Bank of the Republic of Turkey [CBRT]) using data from both the conventional and the new monetary policy episodes. We empirically document that the overnight spread has recently been influenced by various factors that are directly or closely related to the liquidity policy of the CBRT. (JEL E43, E52, C24)