This study aims to investigate the influences of maternal dietary patterns on the triacylglycerol (TAG) composition, particular medium- and long-chain triacylglycerol (MLCT) in human breast milk. A total of 180 Chinese human breast milk samples were collected and divided into three dietary patterns groups accounting to semi-quantitative food intake frequency questionnaire and a 24-hour dietary recall. Using high performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry, 108 TAGs were identified and quantified. In breast milk samples, MLCTs accounted for 25.76 % (median of 24.63%; 95% CI: 24.60, 26.92) of the total TAGs. In human breast milk, the main type of MLCT is TAGs esterified with one medium-chain fatty acid and two long-chain fatty acids (MLL type) which accounted for ~81% of total MLCTs. Among the molecular species of MLCT, O-P-La, O-L-La, and O-L-M are the three most abundant configurations in MLCT (2.28%, 2.17%, and 2.01% of total TAGs, respectively). MLCT in breast milk was positively correlated with the energy supply ratio of carbohydrates (P = 0.205), which was significantly higher than that of the other two groups (P = −0.150 and −0.232).