Public trust in police is central to democratic governance, yet its development during interstate war remains underexplored. Research on crisis-related trust has largely focused on political leaders and the military, leaving civilian security institutions understudied. This paper examines public trust in the Ukrainian National Police from 2015 to 2024, focusing on Russia’s full-scale invasion in 2022. Using nationally representative survey data from the Kyiv International Institute of Sociology (N = 15,059) and an interrupted time-series design, we analyze changes before and after the war’s onset. Results show a sharp increase in trust in 2022, followed by a gradual decline. This pattern aligns with rally-around-the-flag dynamics and suggests that wartime trust surges are temporary. The study contributes to policing research by extending rally-around-the-flag theory to a previously neglected institution in the context of interstate war. © 2026 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.