A tiled display device includes a plurality of display panels coupled to each other, where each of the plurality of display panels includes an edge region adjacent to a boundary line between the plurality of display panels, and a panel driver which multiplies input gray levels of input image data for the plurality of display panels by an adaptive gain, generates boundary compensated image data by adding boundary compensation gray levels to the input gray levels multiplied by the adaptive gain for the edge region, and drives the plurality of display panels based on the boundary compensated image data. The adaptive gain is gradually decreased over a plurality of frame periods in a case where a sum of each of the input gray levels for the edge region and a corresponding one of the boundary compensation gray levels exceeds a maximum gray level.