Abstract: A ceiling vent air diverter is taught, in the preferred embodiment, which incorporates a diverter body configured to cover beneath an existing air vent supplying air to a room of a building. The diverter body has a rectangular flat bottom and upstanding sides with each upstanding side having a discharge air slot permitting air to be distributed in opposed directions from the diverter at a ceiling level. A peripheral flange extends outwardly from each side of the body, in parallel relationship with the bottom and is used for attachment to the building ceiling. A second embodiment is configured and functions in the same manner as above but covers over the top of an existing air vent and includes a lip on the underside of the flange. The third embodiment is for a ceiling air duct diverter system consisting of a box like housing with side walls, an open top and open sides to divert air flow and having the capability of affixing the open top near a ceiling air vent.