With the continued threat of morbidity and mortality from influenza and the development of resistance to influenza antiviral drugs, there is increasing interest in new treatments, such as the investigational intravenous drug peramivir, and in combination treatments. In this study, we determined the impact of oseltamivir carboxylate on the binding affinity of peramivir/neuraminidase (NA) enzyme complex and vice versa. Influenza NA was incubated with peramivir and oseltamivir carboxylate alone and in combination. Dissociation rates of the enzyme-inhibitor complex measured in the presence of NA substrate for peramivir alone and the combination were similar, suggesting that peramivir competitively inhibits the neuraminidase enzyme and that oseltamivir carboxylate when added to peramivir does not impact the binding affinity of peramivir to the NA enzyme.