Background: A visual-verbal integration model (VVIM) was used to train parents and their children with intellectual and developmental disabilities (IDD) to dispense a pea-sized amount of fluoridated toothpaste, aiming to balance the occurrence of dental caries and fluorosis. Method: Participants were 370 pairs of IDD preschool children and their parents. A two-phase pre-post-intervention study was performed. The weight of toothpaste was calculated by a portable electronic compact balance. Results: A quarter of parents and <20% children dispensed the appropriate amount at baseline. Almost 85% parents and 50% children achieved the pea-sized amount after intervention. Half of the children continued to use the recommended toothpaste amount after 6 months. Children with higher intellectual functioning and conceptual skills were more likely to dispense the pea-sized amount of toothpaste. Conclusions: Visual-verbal integration model training had a desired impact on parents' toothpaste-dispensing performance. Children with higher adaptive skills may benefit from VVIM training.