Oral health challenges in preschool children, including plaque accumulation and gingival issues, are often linked to poor brushing habits and limited parental involvement. This study aimed to assess the impact of an educational intervention based on the COM-B (Capability, Opportunity, Motivation – Behavior) model on improving oral health behaviors in children aged 4–6. A clinical controlled trial was conducted in three kindergartens in Isfahan (2022–2023), involving 91 children initially. Participants were assigned to three groups: Group I received an educational package (animated video, instructional content, and reminders), Group II received only a video, while the control group received no intervention. Plaque and gingival indices were measured before and one month after the intervention. Parents completed a toothbrushing behavior checklist and a COM-B-based self-assessment survey. Data from 62 participants were analyzed. Group I showed statistically significant improvements in motivation (14.4 ± 3.4 to 16.1 ± 3.3; P = 0.04) and capability (15 ± 3.3 to 16.9 ± 3.6; P = 0.03). A significant reduction in plaque index was observed in Group I (11.2 ± 6.4 to 6.9 ± 2.3; P < 0.001), with a more marked improvement among female participants. Parental involvement in daily brushing increased, while gingival index changes were not significant. The COM-B-based oral health educational package effectively improved parental motivation, child brushing behavior, and plaque reduction. The COM-B framework shows promise for preschool oral health programs and can be adapted for larger-scale interventions.