Abstract Objectives To describe the different ways in which parents conceive a theory-based behavioural intervention to prevent dental caries in their preschool-aged children. Methods Qualitative interview study using phenomenographic analysis in tenpublic dental clinics in Region Västra Götaland, Sweden (March 2023–July 2024). Ten parents (8 women, 2 men) of 3–6-year-old children at elevated caries risk completed ≥2 counselling sessions with university-trained, health promoters. Interviews (30–60 min) were audio-recorded, transcribed verbatim, and analysed inductively to capture variation in parental conceptions. Flexible delivery (digital/in-clinic) and interpreter support were available. Results This study identified three themes tracing a progression from ambivalence to agency. Three subgroups emerged (1) An offer lined with ambivalence, (2) Empowered alliance through personalised support and (3) Active choices through parental agency. These themes coalesced in the synthesis ‘From ambivalence to agency: embracing health-promoting behaviour’. Conclusions Parents conceived health-promoter-led, theory-based behavioural intervention as non-judgemental, culturally responsive, and practically useful. By fostering relational safety and providing actionable tools, the intervention appeared to strengthen parental self-efficacy and catalyse family-level behaviour change. This shift, while modest in scale, may represent a necessary step toward equitable and sustainable oral health promotion.