Breast milks can be contaminated with perfluoroalkyl substances (PFASs). Exposure to PFASs during early stages of life may lead to adverse health effects among breastfed infants. To date, perfluorootanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have been most frequently measured PFASs in breast milks worldwide. Information on shorter carbon-chain PFASs in breast milk is scarce. In this study, breast milks were sampled from 264 Korean lactating women, and measured for seventeen PFASs, including ten perfluoroalkyl carboxylates (PFCAs), four perfluoroalkyl sulfonates, and three perfluoroalkyl sulfonamides. PFOA and PFOS were detected in 98.5% of the breast milk samples, with median concentrations of 0.072 and 0.050 ng/mL, respectively. Perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), and perfluoroheptanoic acid (PFHpA) were detected in higher frequencies, ranging between 67.4% and 81.8%. The concentrations of short carbon-chain PFCAs in breast milk such as PFPeA and PFHxA were the highest ever reported to date, and were comparable to that of PFOS. Concentrations of shorter chain PFCA in breast milk tended to be higher among the women with longer lactation period, while those of PFOA showed the opposite trend, suggesting a possibility that breastfeeding might be an important route of excretion for PFOA among lactating women. Fish consumption and the use of consumer products, e.g., skin care products, cosmetics and non-stick coated cooking utensils, were identified as significant predictors of PFAS concentrations in breast milk. Health risks associated with PFOA and PFOS exposure through breastfeeding were estimated negligible, however, risks of the short carbon-chain PFCAs could not be assessed because of lack of relevant toxicological information. Further efforts for source identification and exposure management measures for shorter chain PFCAs are necessary.