Aim: To investigate the dynamics of law enforcement officers’ physical and mental health components while performing their duties during the war in Ukraine. Materials and Methods: The research, which was conducted in 2022-2024, involved 114 law enforcement officers (male) from the Kharkiv oblast (Ukraine) of different ages: under 30 (n = 35), under 40 (n = 41), over 40 (n = 38). To test law enforcement officers’ physical and mental health indicators, we used 3 methods: 1) “Fatigue-Monotony-Oversaturation-Stress”; 2) “Well-being-Activity-Mood”; 3) “Assessment of Nervous and Emotional Stress” Results: The negative dynamics of most components of the physical and mental health of law enforcement officers of all three groups while performing their duties during the martial law were revealed. The most pronounced significant changes occurred in such components as “Fatigue”, “Oversaturation”, “Stress”, “Well-being”, “Mood”, “Nervous and Emotional Stress”. The most pronounced negative changes in most components occurred in law enforcement officers over 40 years old, which is due to both the age characteristics of the subjects and their length of service. Conclusions: The research confirms the high complexity and extremity of law enforcement officers’ service activities during the martial law, as well as the high requirements for law enforcement officers’ readiness to perform tasks in the context of a significant expansion of the National Police’s powers. The results obtained also necessitate the search for effective ways to preserve and maintain the physical and mental health of law enforcement officers.