The general benefits model of social support suggests that adolescents who perceive low social support generally experience poorer mental health outcomes; however, less is known of whether adolescents who perceive deficient support from one source may be protected from internalizing difficulties if they are able to access sufficient social support from another source. The current study investigated siblings as a source of support and the potential for social support compensation within the home (i.e., sibling-parent) and school settings (i.e., teacher-classmate), as well as across individuals in these two important settings (i.e., sibling-classmate, parent-teacher). With a sample of 241 high school students (73% female), structural equation modeling examined whether social support compensation would be evidenced in relation to internalizing difficulties. Results indicated that at school the association between low classmate support and internalizing problems was buffered by high teacher support. At home, the association between low parent support and internalizing problems was buffered by high sibling support. Across settings, compensation was evidenced between both adult-based (i.e., teachers and parents) and peer-based (i.e., classmates and siblings) sources of support. Results indicated that although low social support is generally associated with higher internalizing problems, adolescents who are able to access support from other sources may experience fewer mental health challenges. These results highlight the importance of accessing a wide range of supportive relationships at home and school, as supportive relationships may protect against internalizing difficulties both within and across settings. Interventions that facilitate family and school relationships are implicated and will be discussed.