There are some concerns about the adequacy of vegetarian diets for pregnant women, infants, and young children because diets that exclude meat and other animal-based products increase the risk of nutrient deficiencies. The aim of the present study was to assess the nutritional knowledge of parents raising 12- to 36-month-old children on vegetarian diets and to evaluate the children’s diets based on the recommendations formulated in the model food ration. The study involved a questionnaire survey that was completed by 326 women raising their children on various types of vegetarian diets and 198 women raising their children on an omnivorous diet. Mothers raising children on a lacto-ovo-vegetarian diet had the highest nutritional knowledge scores (15.8 points on average), whereas control group mothers and women raising children on a vegan diet had the lowest nutritional knowledge scores (average of 13.6 points). Parents who raised their children on more restrictive vegetarian diets were more aware of the risk of nutritional deficiencies and administered dietary supplements more frequently. A vegetarian diet can be safe for young children, but parents should be educated about the risk of nutritional deficiencies and the principles of healthy nutrition regardless of the administered diet, and effective communication between parents, pediatricians, and dietitians should be the cornerstone of every nutritional strategy in the management of vegetarian children.