The present technology relates to an encoding device and method, a decoding device and method, and a program that enable audio of a high audio quality to be obtained with a smaller code amount.The encoding device multiplexes low frequency encoding data obtained by encoding a low frequency component of an input signal and high frequency encoding data obtained by encoding data including an estimation coefficient to acquire a high frequency component of the input signal by estimation and outputs multiplexed data. When the input signal is encoded, a calculation unit calculates pseudo high frequency subband power to be an estimation value of power of the high frequency component from an estimation coefficient selected in a frame immediately before a frame of a processing target and the high frequency component of the input signal. In addition, a determination unit determines whether reuse of the estimation coefficient of the immediately previous frame is enabled in the frame of the processing target, on the basis of a comparison result of the calculated pseudo high frequency subband power and actual high frequency component power. The present invention can be applied to the encoding device.