Disclosed herein are a method and apparatus for image encoding and decoding using prediction based on a block shape. Whether a prediction mode is available for a target block is determined. The determination is performed based on the shape of the target block. When the prediction mode is determined to be unavailable for the target block, signaling related to the prediction mode may be omitted, and determination of an additional prediction mode is performed. When the prediction mode is determined to be available for the target block, information indicating whether the prediction mode is to be used for the target block is signaled.