<p>Being of immigrant background is a risk factor for poor mental health among youth. In OECD countries such as Australia, Canada and the United States, both immigration and youth are a policy-focus as these countries are popular destinations for immigrants. The purpose of this study was to investigate the mental health of immigrant youth to better support their acculturation and mental health. This study compared the mental health of immigrant youth in Australia, Canada and the United States, and refugee and migrant youth within each country. It also explored numerous factors that were previously reported to impact the mental health of immigrant youth needing to acculturate to their settlement country. The Strengths and Difficulties Questionnaire, a global mental health screen, was used to evaluate 1063 participants recruited through communities in California, Ontario and South Australia. Twenty-four predictor variables were explored, and multivariable linear regression models accounted for substantial proportions of variance in the mental health of immigrant youth in each country. Perceived discrimination, family functioning and resilience were predictive of the mental health of immigrant youth across Australia, Canada and the United States. Additional predictors differed between each settlement country. Similarities and differences in the findings between Australia, Canada and the United States were discussed, and the study provided specific recommendations for policy and practice related to the needs of immigrant youth in the three settlement countries. This study was a timely contribution to the area of youth mental health, whose purpose was to support the acculturation and mental health of youth in OECD countries where great diversity exists due to immigration.</p>