Purpose: Overprotective parenting and its impact on child development has gained increasing public attention. This study explored the association between overprotective parenting and behaviour during dental treatments and toothbrushing behaviour of 4 to 11-year-old-children. Methods: In this cross-sectional study, caregivers of 4-to-11-year-old children who visited a referral practice for dental treatment in Leiden, The Netherlands, completed a questionnaire about overprotective parenting, using the Parental Overprotection Measure (POM), and children’s toothbrushing behaviour. The dentist and dental assistant used the Venham scale to assess children’s behaviour during dental treatments. Associations between the POM and the Venham scale and toothbrushing variables, were analysed using multiple ordered logistic regression. Results: The sample included 96 children (mean age: 7.3 ± 2.1 years, 59 boys). Overprotective parenting (higher POM scores) was significantly associated with more disruptive behaviour of children during dental treatments (higher Venham categories) (OR: 1.08 (95% CI 1.04; 1.13)) and lower caregiver self-efficacy regarding toothbrushing (OR 0.96 (95% CI 0.93; 0.99)), after adjustment for confounders. No associations between overprotective parenting and toothbrushing frequency or skipping toothbrushing were found. Conclusions: Overprotective parenting has been associated with children’s negative behaviour during dental treatments and lower caregiver self-efficacy regarding toothbrushing in primary school children who are treated in a referral practice for paediatric dental care.