M-FSK modulation classification and identification of the modulation order are studied for both flat and frequency selective fading channels. In the modulation classification, M-FSK modulated signals are identified from M-PSK and M-QAM signals using amplitude and spectral features of the received signal. Once the M-FSK signal is identified, then the order of the signal is detected blindly. Various features of the modulated signal are investigated to be able to identify them in practical wireless channels.