This paper describes secondary analysis of previously unreported data collected during the 2014 Australian Human Rights Commission Inquiry into Children in Immigration Detention. The aim was to examine the mental health of asylum-seeking parents and children during prolonged immigration detention and to consider the human rights implications of the findings. The average period of detention was seven months. Data includes 166 Kessler 10 Scales (K10) and 70 Strengths and Difficulties Questionnaires (SDQ) for children aged 3-17 and parental concerns about 48 infants. Extremely high rates of mental disorder in adults and children resemble clinical populations. The K10 indicated severe co-morbid depression and anxiety in 83% of adults and 85.7% of teenagers. On the SDQ, 75.7% of children had a high probability of psychiatric disorder, with lower conduct and hyperactivity scores than clinic populations. Sixty-seven percent of parents had concerns about their infant’s development. Correlations were not found between time detained or parent/child distress. Multiple human rights breaches are identified, including the right to health. This is further evidence of the profound negative consequences for adults and children of prolonged immigration detention. Methodological limitations demonstrate the practical and ethical obstacles to research with this population and the politicized implications of the findings.