BACKGROUND: In the United States, about two thirds of women of reproductive age are overweight or obese. Postpartum is a transitional period. Life changes during this time can put mothers under high levels of stress when interpersonal support is inadequate. This study sought to explore predictors of unmet social support (support inadequacy) for healthy behaviors among postpartum women who were overweight or obese before pregnancy. METHODS: Potential predictors of unmet social support for healthy behaviors were derived from baseline and 6-month postpartum data from the Active Mothers Postpartum (AMP) study. The Postpartum Support Questionnaire queried three dimensions of social support: (1) informational support, (2) emotional support, and (3) instrumental support. The main outcome, the overall Unmet Social Support Score (USSS), was the sum of the differences between the perceived need of support and perceived receipt of support in all three dimensions. Subscores were defined for each of the three support dimensions. RESULTS: One hundred ninety women completed the 6-month Postpartum Support Questionnaire. Depression (p=0.018), unmarried status (p=0.049), and postpartum weight gain (p=0.003) were crude predictors for the overall USSS. After controlling for covariates, depression (p=0.009) and living with a spouse (p=0.040) were significant predictors for overall USSS. In adjusted analysis, depression remained a significant predictor for unmet emotional (p=0.035) and instrumental (p=0.001) social support. CONCLUSIONS: Certain psychosocial factors predict support inadequacy expectations among postpartum women. Targeting the factors related to unmet social support may be a helpful way to promote healthy behaviors among overweight postpartum women.