To examine associations between parental military service and school-based weapon carrying, school-based physical fighting and gang membership among youth. We used cross-sectional data from the 2008 Washington State Healthy Youth Survey collected in 8th, 10th, and 12th grades of public schools (n = 9,987). Parental military service was categorized as none (reference group), without combat zone deployment, or deployed to a combat zone. Multivariable logistic regression was used to test associations between parental military service and three outcomes: school-based weapon carrying, school-based physical fighting and gang membership. Standard errors were adjusted for the complex survey design. In 8th grade, parental deployment was associated with higher odds of reporting gang membership (OR = 1.8) among girls, and higher odds of physical fighting (OR = 1.6), and gang membership (OR = 1.9) among boys. In 10th/12th grade, parental deployment was associated with higher odds of reporting physical fighting (OR = 2.0) and gang membership (OR = 2.2) among girls, and physical fighting (OR = 2.0), carrying a weapon (OR = 2.3) among boys. Parental military deployment is associated with increased odds of reporting engagement in school-based physical fighting, school-based weapon carrying, and gang membership, particularly among older youth. Military, school, and public health professionals have a unique, collaborative opportunity to develop school- and community-based interventions to prevent violence-related behaviors among youth and, ultimately, improve the health and safety of youth in military families. Ideally, such programs would target families and youth before they enter eighth grade.