The human immunoglobulin G (IgG) class is the most prevalent antibody in serum, with the IgG1 subclass being the most abundant. Two glycans are conserved in the Fc region in IgG, however their structural importance on intact IgG1 has been unclear. We subjected glycosylated and deglycosylated human IgG1 to analytical ultracentrifugation, small angle X- ray and neutron scattering, and atomistic modelling. Changes in the cross-sectional radius of gyration and the distance distribution P(r) curve revealed that the Fab-Fc separation has been perturbed following deglycosylation. Atomistic scattering modelling based on Monte Carlo simulations resulted in good X-ray and neutron curve fits. Molecular views of the 100 best-fit models showed that the glycosylated Fc region has a restricted range of conformations relative to the Fab regions, while those in deglycosylated IgG1 showed a broader spectrum of Fc conformations. These more flexible Fc conformations account for the loss of binding to the FcγR receptor in deglycosylated IgG1.