Background: Dental caries persists as one of the most prevalent chronic diseases among children worldwide. In preschool age children, this form of dental caries is termed as Early Childhood Caries (ECC). The objective of this study is to determine the frequency of dental caries among preschool children of Biratnagar, Nepal. Methods: A cross-sectional study of 1382 preschool children was conducted in Biratnagar, Nepal. Children were randomly selected from government run preschools in Biratnagar. Children between 3-6 years age group were assessed for dental caries. Data was analyzed using SPSS version 16.0 software. Results: Out of the 1382 children examined, 894(64.86%) had caries out of which 501(56.04%) were males and 393(43.95%) females. The overall mean deft for ECC was 2.93__ampersandsignplusmn;2.17 ranging from 0-16. Severe-ECC was present in 39.59% (354 out of 894) of caries positive children. Dental plaque was present in 931(67.36%) children. 279(20.18%) children had poor oral hygiene. Conclusion: More than half of the preschool children had early childhood caries. Association between age of the child, dental plaque and poor oral hygiene has been established. There is an urgent need for preventive and curative oral health programs for children in Nepal.