BACKGROUND: Given that relatively little is known about the development of resilience in early childhood, this longitudinal study aimed to identify preschool resource factors associated with young children's mental health resilience to family adversity. METHODS: A community sample of 474 young Australian children was assessed in preschool (mean age 4.59 years, 49% male), and again two years later after their transition into formal schooling. At each assessment, standard questionnaires were used to obtain ratings from both parents and teachers about the quality of children's relationships with parents and teachers, children's self-concept and self-control, mental health (Strengths and Difficulties Questionnaire), and family adversities (including stressful life events and socioeconomic disadvantage). RESULTS: Greater exposure to cumulative family adversities was associated with both greater teacher- and parent-reported child mental health difficulties two years later. Multiple methodologies for operationalizing resilience were used to identify resources associated with resilient mental health outcomes. Higher quality child-parent and child-teacher relationships, and greater child self-concept and self-control were associated with resilient mental health outcomes. With the exception of child-teacher relationships, these resources were also prospective antecedents of subsequent resilient mental health outcomes in children with no pre-existing mental health difficulties. Child-parent relationships and child self-concept generally had promotive effects, being equally beneficial for children facing both low- and high-adversity. Child self-control demonstrated a small protective effect on teacher-reported outcomes, with greater self-control conferring greater protection to children under conditions of high-adversity. CONCLUSIONS: Findings suggest that early intervention and prevention strategies that focus on fostering child-adult relationship quality, self-concept, and self-control in young children may help build children's mental health and their resilience to family adversities.