Borderline personality disorder (BPD) is characterized by a pattern of intense but unstable interpersonal relationships. These interpersonal dysfunctions may originate from impaired bonding and attachment that is determined during early life. Remarkably, it has been reported that the quality of mother-infant relationship is influenced by the feeding mode. Thus, bottle feeding instead of breastfeeding and possible lack of maternal bonding-related behavior may increase the risk for later psychopathology and attachment problems as seen in BPD. A total of 100 BPD patients and 100 matched healthy controls underwent semistructured interviews, based on retrospective information about early risk factors and breastfeeding during infancy. The authors' analyses revealed that BPD patients were significantly less breastfed compared to healthy controls (no breastfeeding in BPD: 42.4%; no breastfeeding in controls: 18.2%; p < .001). The BPD diagnosis was significantly predicted by the variable "no breastfeeding" (p < .001; odds ratio [OR] = 3.32; confidence interval [CI] [1.74, 6.34]), even after adjustment for childhood trauma and several confounding factors (p = .001). The variable "no breastfeeding" accounts for 9.1% of the variance of the BPD diagnosis and is associated with low perceived maternal bonding (p = .006). Breastfeeding may act as an early indicator of the mother-infant relationship that seems to be relevant for bonding and attachment later in life.