<p>Microbial dormancy enables microorganisms to persist under unfavourable conditions and reactivate when ecological or host environments become permissive. While dormancy supports microbial resilience, it also creates cross-domain “hidden reservoirs” that can destabilize ecosystems, amplify zoonotic risk, and sustain antimicrobial resistance (AMR). This narrative review synthesizes evidence across environmental, animal, and human systems to explain how reactivation triggers propagate through One Health pathways—for example, nutrient enrichment or warming in aquatic/soil environments → microbial revival and amplification → exposure in livestock/wildlife → human infection via food, water, aerosols, or vectors. Dormant pathogens can persist in soil, water, sediments, biofilms, and host-associated niches, frequently evading culture-based detection and re-emerging under stressors such as temperature shifts, hydrological change, malnutrition, immunosuppression, and antimicrobial exposure. Dormancy also facilitates AMR persistence through survival of tolerant subpopulations, biofilm protection, and environmental dissemination of resistance determinants. Because key cues governing dormancy–reactivation remain incompletely characterized and surveillance systems rarely target dormant states, outbreak forecasting and mitigation are often delayed. The review therefore proposes dormancy-aware One Health surveillance and response, including field-deployable molecular detection, shared data platforms, and targeted interventions at environmental and veterinary interfaces.</p>