A method and system for detecting and quantifying blockiness in a video file is disclosed. The video file is a file that has been decompressed by using standard DCT algorithms. The method includes segmenting each frame of the video file into multiple blocks. The method also involves comparing the intensity gradients of each block with one or more threshold values. The one or more threshold values represent predefined intensity variation characteristics. Further, the method includes determining the intensity variation parameters of each block, based on the comparison. Thereafter, a blockiness index is calculated for each block, after which a blockiness value is calculated for each frame. Finally, a blockiness level is assigned to each frame, based on its blockiness value. The blockiness level is a comparative measure of the blockiness of a frame that represents the blockiness content in the frame.