--- - |2 Research has established that social support for relationships is an important predictor of well‐being. However, the underlying assumption that social support specifically for relationships is a separate construct from general social support has not been properly tested empirically, nor has the question of whether support processes vary by source (friends vs. family). The current study (N = 1,281) used confirmatory factor analysis and structural equation modeling to address these issues. Support was found for a theoretical model in which social support specifically for relationships predicts relationship well‐being and, in turn, mental and physical health, even while controlling for general social support. Somewhat different patterns were found by source of support (family vs. friends) and by relationship type (same sex vs. mixed sex). - Personal Relationships, Volume 25, Issue 3, Page 374-393, September 2018.