Statement of problem: Early childhood caries can cause pain, discomfort and also inability to have a healthy nutrition .Malnutrition can be characterized when there is a weight, height, and body mass index (BMI) deficiency.Purpose: The aim of this study was to evaluate the relationship between the severe early childhood caries (based on the dmft index) and BMI in pre-school children in Shiraz.Materials and Method: A descriptive analytical cross-sectional study was enrolled on 202 healthy preschool children with the age range of 3-6 years recruited from the kindergartens of different socio- economical parts of Shiraz, Iran. The Anthropometric measurements, weight and height were evaluated. The Z-scores were calculated employing WHO Anthro software (www.who.int/childgrowth/software/en/ index.html) to elucidate the subject’s status on the age- and sex-specific growth chart. Every Child who has received two Z-scores under the normal value (< -2) was considered as abnormal. The relationship between dmft index and BMI was then investigated.Results: The mean of dmft was 4.13. From children with severe early childhood caries, 12.5%were under weight, 5% had height deficiency and 19.5% had BMI deficiency, however, there was no significant relationship between increasing dmft and the height, weight and BMI deficiency.Conclusion: There was not a linear correlation between severe early childhood caries and BMI, height, and weight deficiency. An incidence of 55% was yielded for severe early childhood caries which was an additional finding of this study.Key Words: Preschool children; Body mass index; Dental caries; Software