The OFDM-IDMA scheme has gained popularity in the field of mobile communication because of its numerous advantages, which include its ability to combat multiple access interference and its high efficiency in the transmission of high data rate signals. However, this scheme is sensitive to synchronization errors. Recently, some papers have investigated and reported the impact of carrier frequency offsets on this laudable scheme but without proffering any major solution to this major drawback. Hence, in this paper, an effective linear minimum mean-squared error (MMSE) based synchronization algorithm is employed to mitigate the effect of carrier frequency offset on the OFDM-IDMA scheme. This approach is highly efficient, as it does not increase the overhead and the complexity of the system. The bit error rate performance of the MMSE-based OFDM-IDMA system is therefore presented and analyzed. Simulation results show significant improvement in the overall performance of the system with the application of the MMSE-based synchronization algorithm. Also, the performances of MMSE-based OFDM-IDMA system in both slow and fast fading Rayleigh multipath channel scenarios are presented.