A self-cleaning ultraviolet wastewater disinfection unit and method are provided. The disinfection unit has a wastewater treatment chamber comprising a UV lamp for treating/disinfecting the wastewater. A plurality of pieces of media may be positioned in the treatment chamber. When wastewater is present in the chamber, gas is injected into the wastewater through a gas inlet conduit. The gas agitates the pieces of media in the wastewater to cause the pieces of media to rub against the UV lamp unit to remove matter that has accumulated on the UV lamp unit. The removal of accumulated matter on the UV lamp and other surfaces in the chamber may improve the efficiency and effectiveness of the disinfecting unit. Furthermore, the cleaning operation may be performed automatically at scheduled periods to increase the time between major cleanings of the unit.