The Armed Forces Health Surveillance Branch conducts weekly surveillance of influenza activity among Department of Defense (DoD) populations each influenza season. This report provides a summary of the data from the 2018-2019 influenza season. Ambulatory data for influenza-like illnesses (ILIs), influenza hospitalization data, and lab data for influenza-confirmed cases were used for the surveillance. The 2018-2019 season differed from past seasons in that it was much longer, had a later peak, and the predominant strain of influenza changed from influenza A(H1N1)pdm09 at the beginning of the season to influenza A(H3N2) in the middle of the season. Non-service member beneficiaries accounted for the majority of ILI-related encounters and hospitalizations. However, there were still 149 influenza-related hospitalizations among service members during the 2018- 2019 season. Continued weekly surveillance of influenza among DoD populations is crucial to track increases in activity each season and the potential emergence of new and/or severe influenza subtypes.