Due to its robustness against channel frequency selectivity and the low-complexity implementation using fast Fourier transform (FFT) circuits, multi-carrier code division multiple access (MC-CDMA) systems are well suited for high data rate wireless multimedia services. However, the multiuser interference (MUI) emerges when the mutual orthogonality among users' codes is violated by the frequency-selective channel propagation, and in the presence of the so-termed near-far effects. In order to mitigate MUI, we present a joint algorithm which combines transmitter power control, receiver array processing and multiuser detection. The joint algorithm exploits both the multipath diversity and the spatial diversity, where the former is provided by the frequency selectivity and the latter is provided by appropriate spacing among the receiver antenna array elements. Simulations confirm the outstanding performance of the joint algorithm in MUI suppression. In addition, we observe that the algorithm provides the best performance when the propagation channel is frequency-selective and the channel fading is independent across different receiver antenna array elements.