We address the problem of carrier frequency offset (CFO) in Orthogonal Frequency Division Multiplexing (OFDM) communications systems in the context of Interleaved Division Multiple Access (IDMA).We propose a technique to adapt a method of blind CFO estimation, called CFO estimation-Syndrome Function Minimization (C-SFM), to the context of a system combining IDMA and OFDM where a quasi-static Rayleigh fading multipath channel is considered. Performance in terms of Mean Squared Error (MSE) of carrier frequency offset is studied for a different number of users. In order to evaluate the robustness of the C-SFM method, we compare the performance of OFDM-IDMA system using C-SFM technique with that of a perfect synchronous system. Our results show that, for high Eb/N0, the two systems have the same performance.