A unified dual-mode global system for mobile communication (GSM)/universal mobile telecommunication systems (UMTS) clock and a transceiver employing the unified GSM/UMTS clock are disclosed. A reference clock generates a reference clock signal and a local oscillator (LO) generates a LO signal based on the reference clock signal. A frequency divider selectively generates either a GSM clock signal or a UMTS clock signal by converting a frequency of the LO signal by a predetermined factor. Both the GSM clock signal and the UMTS clock signal are generated based on the common reference clock signal. The reference clock signal frequency may be a GSM fundamental frequency or a UMTS fundamental frequency. An interpolator and/or a decimator may be used for matching frequencies of UMTS baseband signal and the UMTS clock signal or frequencies of GSM baseband signal and the GSM clock signal.