Many new moms express a desire to be physically active but encounter a variety of barriers, the most common being lack of perceived social support. Different types of support might be needed for new mother to be active (e.g., for exercise- or postpartum-related barriers).While social support (SS) has been shown to improve physical activity and well-being, there is a need to understand moderators of these relationships. Exercise-related cognitive errors (ECEs) bias how accurately individuals view their physical activity and might impact the support-activity relationship. It was hypothesized that ECEs and SS would interact to predict physical activity and psychological wellbeing in the first year after giving birth. New moms (N= 268, Mage=29.96) completed a self-reported survey using the ECE questionnaire (ECE-Q), Social Support for Exercise scale (SSES; subscale Family), a modified Postpartum Support questionnaire (PSSQ; Subscale Family), and Psychological Wellbeing scale (PWBS), and moderate-to-vigorous physical activity (MVPA). SSES (B= .258, p < .001) and the ECE-Q (B= .130, p= .036) predicted MVPA (R2=.07, p < .001) beyond covariates. SSES (B= -. 146, p=.023), PSSQ (B= .461, p<.001), and the ECE-Q (B= -.145, p= .009; predicted PWBS (R2=.24, p < .001) beyond covariates. None of the interactions were significant. While previous research has observed an interaction between SSES and ECEs in predicting MVPA during pregnancy, the current findings did not support this interaction after birth for new mothers. Findings underscore possible predictors of how mothers view and overcome their physical activity barriers and of their wellbeing.