Many studies have used mobile device location data to model SARS-CoV-2 dynamics, yet relationships between mobility behavior and endemic respiratory pathogens are less understood. We studied the impacts of human mobility on the transmission of SARS-CoV-2 and 16 endemic viruses in Seattle over a 4-year period, 2018-2022. Before 2020, school-related foot traffic and large-scale population movements preceded seasonal outbreaks of endemic viruses. Pathogen circulation dropped substantially after the initiation of stay-at-home orders in March 2020. During this period, mobility was a positive, leading indicator of transmission of all endemic viruses and lagged SARS-CoV-2 activity. Mobility was briefly predictive of SARS-CoV-2 transmission when restrictions relaxed in summer 2020 but associations weakened in subsequent waves. The rebound of endemic viruses was heterogeneously timed but exhibited stronger relationships with mobility than SARS-CoV-2. Mobility is most predictive of respiratory virus transmission during periods of dramatic behavioral change, and, to a lesser extent, at the beginning of epidemic waves.