The relationship between early childhood caries (ECC) and obesity is controversial. This cross-sectional survey investigated this association in children from low-income families in Goiania, Goias, Brazil and considered the role of several social determinants. A questionnaire examining the characteristics of the children and their families was administered to the primary caregiver during home visits. In addition, children (approximately 6 years of age) had their height, weight, and tooth condition assessed. The primary ECC outcome was categorized as one of the following: caries experience (decayed, missing, filled tooth: "dmft" index > 0), active ECC (decayed teeth > 0), or active severe ECC (decayed teeth ≥ 6). Descriptive, bivariate and logistic regression analyses were conducted. The participants in the current study consisted of 269 caregiver-child dyads, 88.5% of whom were included in the Family Health Program. Caregivers were mostly mothers (67.7%), were 35.3 ± 10.0 years old on average and had 9.8 ± 3.1 years of formal education. The mean family income was 2.3 ± 1.5 times greater than the Brazilian minimum wage. On average, the children in the current study were 68.7 ± 3.8 months old. Of these, 51.7% were boys, 23.4% were overweight or obese, 45.0% had active ECC, and 17.1% had severe ECC. The average body mass index (BMI) of the children was 15.9 ± 2.2, and their dmft index was 2.5 ± 3.2. BMI was not associated with any of the three categories of dental caries (p > 0.05). In contrast, higher family incomes were significantly associated with the lack of caries experience in children (OR 1.22, 95%CI 1.01-1.50), but the mother's level of education was not significantly associated with ECC.