BackgroundTemperament associated with oral health behaviour and early childhood caries (ECC) in preschoolers remains inconclusive.AimThis cross‐sectional study investigated the association of temperament with oral health behaviour and ECC status.DesignA total of 421 Thai preschoolers were recruited from elementary schools in Chonburi Province, Thailand. Their caregivers assessed three temperament dimensions (surgency, negative affectivity and effortful control) using the Thai version of the Children's Behaviour Questionnaire Very Short Form and reported oral health behaviours (brushing cooperation and cariogenic snack frequency). Three calibrated dentists assessed ECC status using the modified WHO dmft/dmfs (decayed, missing and filled teeth/surface) index that included noncavitated and cavitated carious lesions.ResultsMultiple regression analysis, after adjusting for child's and caregiver's characteristics, revealed that children with high negative affectivity or low effortful control were more likely to have uncooperative brushing behaviour. The temperament scores of children who consumed cariogenic snacks daily and those who did not were comparable. Children with low surgency, high negative affectivity or low effortful control were more likely to have high dmfs scores.ConclusionNegative affectivity and effortful control were associated with brushing behaviour. Temperament was not associated with the frequency of cariogenic snack consumption. All temperamental dimensions, however, were associated with ECC.