Multi-carrier code division multiple access (MC-CDMA) systems are well suited for high data rate wireless multimedia services due to their capability of converting the frequency-selective jading channels to distinct frequency-flat ones with, low-complexity fast Fourier transform (FFT) devices. However, in multiuser MC-CDMA systems, the frequency selectivity and variation of the users ' geographical locations give rise to the multiuser interference (MUI) which induces a significant performance degradation of the systems. In order to mitigate MUI, we present a joint interference suppression algorithm of transmitter power control, receiver array processing and multiuser detection. In addition to the interference suppression using this algorithm, the frequency selectivity also provides multipath diversity if appropriately exploited. Simulations confirm the outstanding performance improvement of this algorithm compared with existing alternatives in MC-CDMA systems, and also confirm that the algorithm performs better in frequency-selective fading channels than m frequency-flat fading ones due to the multipath diversity.