A catch basin sealing system for closing a basin opening in a catch basin to inhibit contaminants from entering the catch basin includes a plurality of guide channels. Each of the guide channels is coupled to a bottom surface of a catch basin. The guide channels are positioned on opposing sides of a basin opening. A closing plate slidably engages the guide channels. The closing plate is slid from a first position adjacent the basin opening to a second position under the basin opening to close the basin opening and inhibit flow of liquid into the catch basin. A seal is coupled to an upper surface of the closing plate. The seal engages the catch basin around the basin opening to inhibit liquid flowing between the closing plate and the catch basin when the closing plate is positioned in the second position.