In this study, eight common and two unusual synthetic phenolic antioxidants (SPAs), as well as four transformation products (TPs), were comprehensively analyzed in 80 human breast milk samples collected from lactating women in South China. All 10 SPAs and 4 TPs were detected in the breast milk samples. 2,4-Di-tert-butylphenol (DBP) was detected at high concentrations (mean of 16.9 ng/mL), followed by 2,6-di-tert-butyl-hydroxytoluene (BHT) (mean of 1.52 ng/mL). DBP and BHT collectively contributed to 91.9% of the mean ∑SPAs (sum concentrations of all 10 detected SPAs). The lipid content was identified as an important endogenous factor that influenced the levels of DBP and BHT in breast milk. The concentrations of BHT, DBP, and ∑TPs (sum concentrations of all four detected TPs) in the breast milk were significantly associated with maternal education level, eating habits, and personal care product use (p < 0.05). Furthermore, the concentrations of BHT and its TPs in the breast milk were also found to be significantly associated with newborn birth outcomes, including prematurity and birth length (p < 0.05). This is the first study to report significant associations of the concentrations of some SPAs in breast milk with some important demographic characteristics and lifestyle factors.