The present invention provides a chlorine retention reservoir for a toilet. The chlorine retention reservoir comprises a housing having a base and a sidewall forming an interior volume with an open upper end. The open upper end includes a lip extending perpendicularly from the sidewall disposed around a perimeter thereof, wherein the lip receives a channel of a lid. The housing further includes an input port and an output port that receive a liquid therethrough. A plurality of baffles are disposed within the interior volume of the housing. A slot is disposed on an exterior surface of the housing, wherein the slot receives a fastener. The fastener removably secures the housing to an interior surface of a tank of a toilet. A chlorine tablet is placed within the housing where it is subjected to incoming water from a flush creating a chlorine solution that is discharged to a toilet bowl.