Aberrant glycosylation is highly associated with cancer progression. The aim of this study was to compare bifucosylated N -glycans in sera obtained from healthy controls and breast cancer patients, with the goal of identifying a potential indicator for monitoring the recurrence and metastasis of breast cancer. A unique structural pattern of bifucosylated N -glycan, with both core and antennary fucosylation, was identified in breast cancer patients. The spectrum of antennary fucosylation was a composite of the standard spectra of Lewis X and H2, indicating a mixture of the two epitopes. Permethylated N -glycans of the glycoproteins extracted from 91 breast cancer patients and 43 healthy controls were detected using linear ion-trap quadrupole-electrospray ionization mass spectrometry, which appeared to be a highly sensitive and useful approach in the detection and identification of N -glycans. To evaluate MS profile data, several statistical tools were applied, including Student's t -test, partial least squares discriminant analysis and receiver-operating characteristic curve. The results showed that the measurement of bifucosylation degree and CEA levels had an improved diagnostic performance compared with that of CEA alone. We compared the potential of bifucosylated N -glycan as an indicator of breast cancer recurrence with the current clinical biomarkers, i.e., CEA, CA 15-3 and CA125. The result revealed that, compared with CEA, CA 15-3 and CA125, the bifucosylation degree of N -glycans could be a more reliable indicator of breast cancer recurrence.