Introduction: Dietary supplements have become a common practice, including among children. It is worth noting that supplementation can have a twofold effect: a pro-health effect – improving the nutritional status of the body, or a harmful effect – increasing the risk of nutrient overdose, such as when several preparations are used simultaneously. Objective: The aim of the study was to assess the determinants of dietary supplement consumption by children aged 3-10. Material and Methods: The study used a questionnaire method among parents of 151 children attending kindergarten and elementary schools in the Mazovia Province. Results: Dietary supplements were used by 54.3% of the children surveyed the year before the study. Women with a university education were significantly more likely to supplement their children than women with a secondary or primary education (60.6% and 42.3%, respectively). More children with normal body weight (58.6%) were given supplements than those with overweight and obesity (27.3%). The vast majority of children (66%) took one supplement daily. Concomitant use of supplements with fortified products was observed in 71.4% of respondents. The decision to use a supplement was mainly made by the parents themselves (62%). Conclusions: Educating parents about the benefits and risks of using dietary supplements is necessary. The use of such preparations should be consulted with a specialist, i.e., a doctor or dietician. It is worth noting that a well-balanced diet should provide all the nutrients, vitamins, and minerals for the child’s proper development.