The present invention provides antibodies that bind to the T-cell co-inhibitor ligand programmed death-ligandl (PD-L1) protein, and methods of use. In various embodiments of the invention, the antibodies are fully human antibodies that bind to PD-L1. In certain embodiments, the present invention provides multi-specific antigen-binding molecules comprising a first binding specificity that binds to PD-L1 and a second binding specificity that binds to a tumor cell antigen, an infected cell-specific antigen, or a T-cell co-inhibitor. In some embodiments, the antibodies of the invention are useful for inhibiting or neutralizing PD-L1 activity, thus providing a means of treating a disease or disorder such as cancer or viral infection.