Children living in Defence families affected by parental mental illness face increased stressors, pressure for self-sufficiency and potential exposure to adverse outcomes, including future mental illness. Little is known about the impact of mental health early interventions on the help-seeking tendencies of military young people affected by parental mental illness. Similarly, the responsivity of this cohort to peer-based mental health literacy interventions aimed to dispel misconceptions and stigmatising beliefs about mental illness and help-seeking is not well understood. The current study measured key aspects of belief-related mental health knowledge and intentions to seek help from a range of formal and informal sources of 236 Australian young people aged 7-18 years, living with parents affected by military-associated mental health problems. Findings suggest that young people in the Defence community are most likely to seek help from their parents and show changes in beliefs about mental illness and intentions to seek help from some help sources following a brief (2-hour) group intervention. Help-seeking intentions from telephone helplines increased for the cohort, and males were more inclined to seek help from a friend after intervention.