ยฉ 2015, American Society for Microbiology. Middle East respiratory syndrome (MERS) is a highly lethal pulmonary infection. Serum from convalescent MERS patients may provide some benefit but is not readily available. In contrast, nearly all camels in the Middle East have been infected with MERSCoV. Here, we show that sera obtained from MERS-immune camels augment the kinetics of MERS-CoV clearance and reduce the severity of pathological changes in infected lungs, with efficacy proportional to the titer of MERS-CoV-neutralizing serum antibody.