This systematic review updates the findings of Bravi et al. (2015) by critically assessing differences in study designs and sampling methods, and graphically visualizing trends and associations. The review focuses on the relationship between maternal diet and human milk composition, particularly fatty acids, carbohydrates, proteins, vitamins, and minerals. A PubMed search was conducted for articles published between January 2015 and March 2021. Twenty-seven observational studies and five intervention studies (n = 7,138) were identified and combined with the results of Bravi et al. The review found that fatty acids remain the most studied components of human milk in relation to maternal diet, with maternal fish intake positively associated with milk ALA, DHA, and EPA content. PUFAs from diet were generally positively correlated with their concentrations in milk, while SFA intake was negatively associated with several fatty acids. Studies on associations with maternal diet and milk carbohydrates, proteins, vitamins, and minerals were limited in number and varied in methods and results. The review concludes that evidence on the association between maternal diet and human milk fatty acids is rapidly increasing but still diversified in methodology and results. Further studies, preferably intervention studies, are needed to draw conclusions on the importance of maternal diet for human milk composition as a whole.This systematic review updates the findings of Bravi et al. (2015) by critically assessing differences in study designs and sampling methods, and graphically visualizing trends and associations. The review focuses on the relationship between maternal diet and human milk composition, particularly fatty acids, carbohydrates, proteins, vitamins, and minerals. A PubMed search was conducted for articles published between January 2015 and March 2021. Twenty-seven observational studies and five intervention studies (n = 7,138) were identified and combined with the results of Bravi et al. The review found that fatty acids remain the most studied components of human milk in relation to maternal diet, with maternal fish intake positively associated with milk ALA, DHA, and EPA content. PUFAs from diet were generally positively correlated with their concentrations in milk, while SFA intake was negatively associated with several fatty acids. Studies on associations with maternal diet and milk carbohydrates, proteins, vitamins, and minerals were limited in number and varied in methods and results. The review concludes that evidence on the association between maternal diet and human milk fatty acids is rapidly increasing but still diversified in methodology and results. Further studies, preferably intervention studies, are needed to draw conclusions on the importance of maternal diet for human milk composition as a whole.