Women who are overweight or obese have increased health risks during and beyond pregnancy, with consequences for their infants' shorter and longer term health. Exclusive breastfeeding to 6 months has many benefits for women and their infants. However, women who are overweight or obese have lower rates of breastfeeding intention, initiation, and duration compared with women with normal weight. This systematic review aimed to examine evidence of (a) breastfeeding barriers and support experienced and perceived by women who are overweight or obese, (b) support shown to be effective in increasing breastfeeding initiation and duration among these women, and (c) perceptions of health care professionals, peer supporters, partners, and family members regarding providing breastfeeding support to these women. Sixteen quantitative and qualitative papers were included and critically appraised. Thematic synthesis was undertaken to obtain findings. Maternal physical barriers such as larger breasts, difficulties of positioning to breastfeed, delayed onset of lactation, perceived insufficient supply of breast milk, and impact of caesarean birth were evident. Maternal psychological barriers including low confidence in ability to breastfeed, negative body image, embarrassment at breastfeeding in public, and experiencing stigma of obesity were also described. Support from health care professionals and family members influenced breastfeeding outcomes. Education for maternity care professionals is needed to enable them to provide tailored, evidence-based support to women who are overweight or obese who want to breastfeed. Research on health care professionals, partners, and family members' experiences and views on supporting this group of women to breastfeed is needed to support development of appropriate interventions.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.