Army National Guard Age Limit: Check Your Enlistment Window If you have no prior military service, you can generally enlist in the Army National Guard from age 17 through age 42. Applicants who are 17 need parental consent. If you served before, or want to become an officer, different age rules may apply. A Guard recruiter can check your service record and the requirements … [Read more...] about 5 Critical Rules About the Army National Guard Age Limit You Need to Know