The present invention provides an alpha blending unit that is able to perform alpha blending on sub-samples of a pixel in an efficient manner. The alpha blending unit preferably comprises a plurality of registers for storing a source color, a blending value, and a plurality of destination sub-sample values, multipliers, adders, an accumulator and a divider. The alpha blending unit advantageously sums the destination sub-sample values and then divides them by the number of sub-samples to generate a combined destination color value. This combined destination color value along with the source color and a blending value are then provided to the multipliers, and adders to generate a new destination color value for the pixel.