Network coded cooperative (NCC) systems have recently gained increasing attention due to their high power and spectral efficiency. For high speed data transmission over frequency-selective channels, NCC is further combined with orthogonal frequency division multiple access (OFDMA). In this paper, we derive outage probability and diversity gain of NCC-OFDMA systems in the presence of carrier frequency offset (CFO). Our results demonstrate that NCC-OFDMA system is capable to achieve full spatial and frequency diversity in noise limited system where the CFO variance sigma(2)(epsilon) -> 0. However, in interference limited case where the CFO variance sigma(2)(epsilon) > 0, error floor occurs leading zero diversity gain. Numerical results are further presented to validate our analytical findings.