This study investigated the concentrations of per- and polyfluoroalkyl substances (PFASs) in the breast milk of 201 Korean mothers and their potential impact on infant growth. Despite regulatory efforts, certain PFAS have shown increasing trends with levels higher than those reported in many other countries. The geometric mean concentrations of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in breast milk were 0.098 and 0.085 ng/mL, respectively. Notably, PFOS (0.085 ng/mL) and perfluorononanoic acid (PFNA) (0.023 ng/mL) concentrations were significantly higher in obese mothers (BMI ≥ 25 kg/m²), correlating with reduced weight-for-length values in male infants (β = –0.53, p = 0.024 for PFOS; β = –0.60, p = 0.006 for PFNA). The estimated daily intake of PFASs in breastfed infants was 17.53 ng/kg bw/day for PFOA, 13.37 ng/kg bw/day for PFOS, and 4.36 ng/kg bw/day for PFNA, exceeding previous domestic reports. Sensitivity analysis showed that the PFAS concentration in breast milk was the most influential factor affecting oral exposure. Considering the endocrine-disrupting properties and sex-specific effects of PFASs, targeted regulatory measures are crucial. Future research should employ longitudinal designs with larger cohorts to better assess the long-term health risks and develop effective mitigation strategies for high-risk populations.