The present study focuses on a positive aspect of resilience among siblings of persons with major mental illness. A cross-national sample of 68 U.S. siblings and 62 Japanese siblings was analyzed to explore the role of social support that may play in their positive experiences, particularly in the domain of self development or growth. Multiple regression analysis revealed a significant positive relationship between the two variables, suggesting that those who have had more social support are likely to gain more sense of growth out of their mental illness-related experiences. Implications for mental health practice have been discussed.