The present technology relates to a signal processing device, a signal processing method, and a program capable of appropriately demodulating a desired signal from a multiplexed signal obtained by multiplexing a plurality of signals. A preamble signal is detected from a multiplexed signal obtained by multiplexing a plurality of signals. When information for discriminating each of the signals that is contained in the preamble signal indicates a first signal, demodulation by a demodulator is continued and the first signal is demodulated. When information for discriminating each of the signals that is contained in the preamble signal indicates a second signal, demodulation is not performed by stopping the demodulation by the demodulator. The present technology can be applied to a signal processing device that processes signals for digital broadcasting.