ManTech International is seeking a Windows System Administrator to support mission‑critical Information Technology operations within our Defense & Aerospace programs. In this role, you will help ensure the availability, performance, and security of Windows‑based systems that enable national security missions across the U.S. intelligence community, Department of Defense, and other federal agencies. As a key member of our IT team, you will install, configure, and maintain Windows Server operating systems and core Microsoft services, including Active Directory, Group Policy, DNS, and DHCP, in both classified and unclassified environments. You will monitor system health, troubleshoot complex issues, and perform root‑cause analysis to sustain high system uptime and reliable performance for users and mission applications. Working closely with cyber security engineers, you will implement and maintain secure baselines in accordance with Department of Defense and federal security policies, including DISA STIGs and related hardening guidelines. You will apply patches and updates, manage access controls, support audit and accreditation activities, and contribute to the overall security posture of ManTech’s critical systems. Automation using PowerShell and other tools will be a core part of your responsibilities, helping streamline repetitive tasks and enforce consistent configurations. This position operates within ManTech’s culture of innovation, integrity, and respect for individual contributions. You will collaborate with network, cyber, and application teams to design and deliver resilient, scalable Windows solutions that support advanced cyber security and defense missions. You will also create and maintain documentation, standard operating procedures, and configuration records to support compliance, continuity, and knowledge sharing across the team. The ideal candidate brings solid Windows administration experience in a secure or regulated environment, strong troubleshooting skills, and familiarity with cyber security principles and DoD or federal standards. Relevant certifications such as Microsoft, CompTIA Security+, or DoD 8570 baseline credentials are highly valued. In joining ManTech, you will have the opportunity to support the development and protection of cutting‑edge national security systems while advancing your technical career in a dynamic, mission‑driven environment.