Background: The correct nutrition of infants is crucial for their proper mental and physical development, as well as for adequate metabolic programming. Programming is the influence of environmental factors, including nutrition, during critical periods of early development (including fetal life and the first years of life) on the risk of disease in adulthood. Objective: The aim of the study was to investigate the level of knowledge of mothers on infant feeding. Material and Methods: The study involved 1100 mothers of different ages who were active in online groups interested in maternity and infant feeding. The inclusion criterion for the study was having a child born between 2021 and 2023. The study used a CAWI (Computer-Assisted Web Interview) method and the survey was conducted in November 2024. Results: It was shown that most of the mothers surveyed had very good knowledge of infant feeding. A good level of knowledge was recorded among younger mothers of children under 6 months of age, with primary/high school education and living in rural areas. Conclusions: It is recommended to provide more detailed information on expanding the diet of infants after 6 months of age, e.g. on the labels of foods dedicated to children.