We used coordinated mutagenesis, synthetic design, and flexible docking to investigate the structural mechanism of Env gp120 encounter by peptide triazole (PT) inactivators of HIV-1. Prior results demonstrated that the PT class of inhibitors suppresses binding at both CD4 and coreceptor sites on Env and triggers gp120 shedding, leading to cell-independent irreversible virus inactivation. Despite these enticing anti-HIV-1 phenotypes, structural understanding of the PT-gp120 binding mechanism has been incomplete. Here we found that PT engages two inhibitor ring moieties at the junction between the inner and outer domains of the gp120 protein. The results demonstrate how combined occupancy of two gp120 cavities can coordinately suppress both receptor and coreceptor binding and conformationally entrap the protein in a destabilized state. The two-cavity model has common features with small molecule gp120 inhibitor binding sites and provides a guide for further design of peptidomimetic HIV-1 inactivators based on the PT pharmacophore.