Multiband / simultaneous multislice increases the temporal resolution in resting-state fMRI but at the cost of noise amplification, which may result in erroneous estimates of correlation-coefficient based functional connectivity. We examined functional connectivity in resting-state scans from ten subjects with multiband factors ranging from two to twelve. The standard deviation of voxel time series varies across space, which is in part due to noise amplification. Multiband acceleration tends to decrease estimates of functional connectivity, particularly for correlations involving subcortical regions. Consequently, it may be challenging to disentangle low neural activity from high noise amplification.