An increasing number of culturally and linguistically diverse (CALD) students from migrant and refugee backgrounds are enrolling in schools in the West. These students are exposed to challenges that may influence their mental health and wellbeing. At the same time, schools tend to play a critical role in promoting these students' social relatedness through a sense of support, connectedness, and an adaptation to the new setting. The aim of the study was to assess the role of social relatedness in promoting mental wellbeing. Resilience was hypothesised as a facilitator process enhancing the relationship between social relatedness and the mental wellbeing of CALD students. Recently arrived CALD students (N = 221) enroll ed at a specialised high school in Australia completed a battery of measures assessing: social support, school connectedness, acculturation, resilience, and mental wellbeing. A series of hierarchical regression analyses indicated that the three social relatedness factors (social support, school connectedness, and acculturation) were related to mental wellbeing. However, their variance decreased when resilience was added. Mediation analyses indicated that resilience was a partial mediator for the relationship between each of the social relatedness elements and mental wellbeing. Resilience was also shown to play a significant role in the relationship between social relatedness and mental wellbeing. School-based mental health services for CALD students from migrant and refugee backgrounds may benefit by further understanding the unique factors that influence the mental wellbeing of children.