Background Vitamin D deficiency has been highlighted as a serious public health problem in the United Kingdom. One in four toddlers are not achieving the recommended intake for their healthy development. This study uses quantitative and qualitative methods to explore parents’ perceptions, awareness and behaviours around vitamin D intake, and the acceptability of and factors affecting purchasing of food and drink fortified with Vitamin D in children aged 0–2 years old. Methods One hundred and ninety-four parents completed an online questionnaire, advertised to parents with one child aged up to 2 years on popular social media websites. The majority of participants were mothers, White-British ethnic background, aged 25–44 years. Participants provided an email address if they wanted to be contacted about the focus groups. Recruitment posters advertising the focus groups were placed in community centres. Eighteen participated in 5 focus groups (13 parents), and 5 individual interviews. A thematic analysis methodology was applied. Results Fifty-seven percent ( n = 110) of parents reported receiving information about vitamin D during pregnancy and 52% ( n = 100) after the birth of their child. Parents reported a low level of satisfaction with vitamin D information: many thought it was limited and recommendations on supplements were unclear. Parents wanted more information about vitamin D requirements for their child (80%, n = 153 out of 192 respondents, 2 non-response), about vitamin D and breastfeeding (56%, n = 108) and vitamin D and pregnancy (49%, n = 94). The recommendations were for simpler, easier to read, with specific and clearer guidelines; delivered regularly during routine appointments, at timely stages throughout pregnancy and after the birth. 23% ( n = 45, out of 194 respondents) of parents did not know why vitamin D is important for health. Only 26% ( n = 49, out of 192 respondents) of parents reported giving their youngest child a vitamin D supplement on most days of the week. The majority of parents (interview/focus group) wanted more information about foods/drinks fortified with vitamin D. Conclusion Parents were generally not aware of the importance of vitamin D, dietary requirements including supplementation and the availability of vitamin D fortified foods. Major improvements are required for the effective promotion of vitamin D information to parents. Electronic supplementary material The online version of this article (10.1186/s12889-019-7340-x) contains supplementary material, which is available to authorized users.