Mild cognitive impairment (MCI) refers to the clinical state of subjects who suffer from some degree of cognitive deterioration but do not meet clinical criteria for dementia. The aim of this study was to analyze the magnetoencephalogram (MEG) background activity in MCI subjects using two connectivity measures: coherence and synchronization likelihood (SL). Our results showed that coherence and SL mean values were lower in the MCI group than in control group at all frequency bands (delta, theta, alpha-1, alpha-2, beta, and gamma). Significant differences were found in the beta frequency band with both measures ( p < 0.05, Mann-Whitney U-test). Coherence analysis also revealed significant differences between controls and MCIs in the gamma band. Additionally, coherence and SL mean values at each frequency band were analyzed by means of receiver operating characteristic curves. The highest accuracy (69.8%) was achieved in the beta band with both connectivity measures. Our results suggest that spontaneous MEG rhythms show disconnection problems in MCI, especially in the beta band. In conclusion, both coherence and SL may be useful measures for discriminating MCI patients from control subjects.