Although preventable, early childhood caries (ECC) is a burdening condition in all WHO regions, with Poland being one of the most affected countries in Europe. Effective home-based prevention of ECC is available and recommended by several expert bodies. Therefore, we wanted to determine how well parents were following selected oral health recommendations in preschool children. Additionally, we wanted to determine which socioeconomic factors influenced such practices the most, and how parents’ oral health literacy and behaviours affected the oral hygiene and oral health status of their children. A cross-sectional survey involving 2338 parents and caregivers of children from 167 kindergartens was performed. Children’s oral hygiene and oral health status were found to be associated with parents’ education and economic status. They were also strongly influenced by parental health literacy and behaviours. With respect to recommendations for preschoolers, the lowest adherence was found in the use of fluoride toothpaste and its age-appropriate amount, supervision of toothbrushing, and refraining from eating after last toothbrushing. The improvement in these areas could be achieved thanks to the involvement of health professionals such as gynaecologists, midwives, and primary care personnel in efforts aimed at increasing parents’ oral health knowledge and literacy.