Background: Military personnel operate in physically and psychologically demanding environments, prompting widespread use of dietary supplements (DSs) to support performance, recovery, and health. The prevalence, motivations, and safety of DS use vary by demographic and occupational factors. To systematically review the prevalence, patterns, motivations, and implications of dietary supplement use in military populations in different countries and service branches. Methods: A systematic search was conducted using PubMed, Scopus, and Google Scholar for articles published from 2000 onward. Studies were included if they reported on active-duty military personnel, provided data on DS use, and employed observational or mixed-methods designs. Data were extracted on prevalence, types of supplements, demographic subgroups, and motivations. A total of eight studies were included. Results: DS use prevalence ranged from 53% to 85%, with higher rates in elite units and younger soldiers. Frequently used supplements included multivitamins, proteins, creatine, and stimulants. Motivations included health maintenance, energy, muscle development, and occupational demands. Several studies reported adverse effects, regulatory gaps, and misinformation regarding supplement use. Conclusion: DS use is prevalent in military populations, exceeding civilian rates. While some supplements address legitimate needs, others pose health risks. Military institutions implement targeted education, regulation, and monitoring strategies to ensure safe and informed use.