Background and aim: The effect of different nutritional pattern consumption patterns in infants on the formation of dental occlusion is one of the issues under discussion. Due to the lack of specific results in this regard, the purpose of this study was to determine the occlusion of deciduous teeth in breastfed and bottle-fed preschool children. Materials and methods: This is a descriptive-analytical study on 316 children aged 4-5 years old. This study was based on clinical examination and completing questionnaire. The examination was done at kindergartens and in sitting position using a dental mirror and with under the natural light to natural light. The occlusal relationship, overjet, overbite, and crossbite were examined through direct observation in the centric occlusion. The questionnaires were completed by the mothers. The basis of this study was the responses that mothers gave in the questionnaire based on the type and duration of breastfeeding or bottle-feeding. The collected data were statistically analyzed by Chi-square test. Significance was considered at the level of P<0.05. Results: The results of this study showed a significant relationship between nutrition with formula and increased overjet (P=0.048) and distal step occlusion (P=0.001). The duration of milk consumption showed no significant relationship with any of the studied variables. Conclusion: Malocclusion was more frequently observed in bottle-fed children.