<p>Adolescent well-being is influenced by a range of individual, familial, and structural factors. While immigration status is often treated as a key determinant, its relative contribution compared to other predictors remains uncertain. Using nationally representative data from the 2019–2020 Canadian Community Health Survey, we examined five well-being indicators including perceived mental health, general health, life satisfaction, perceived stress, and sense of community belonging among adolescents aged 12–17 (<i>N</i> = 6,499). Mann–Whitney U tests compared immigrant and non-immigrant youth, and multivariable ordinal logistic regression assessed associations with gender, household income, household education, and physical activity. Immigrant youth reported lower perceived mental health, general health, and community belonging, but also lower stress levels compared with non-immigrants. In adjusted models, immigration status was not an independent predictor of well-being. Gender and physical activity emerged as the most consistent determinants: female adolescents reported poorer mental health and higher stress, while physically active youth had better outcomes across multiple domains. Household income showed a complex pattern—lower income predicted poorer mental health but, unexpectedly, higher life satisfaction. Household education was not a significant predictor. Findings should be interpreted cautiously because the dataset’s binary variables on immigration and race/ethnicity omit population heterogeneity, including distinctions between racialized and white immigrants. Results highlight the importance of modifiable social and behavioral determinants in adolescent well-being and support equity-oriented interventions that promote inclusive physical activity, address gendered mental health disparities, and foster community belonging.</p>