The prevalence of dental decay is expected to rise in many developing countries due to the growing consumption of sugars. This study aimed to assess knowledge, attitudes and practices of sweet food and beverage consumption among schoolchildren in Jazan, Saudi Arabia and to determine the relationship with dental caries. In a cross-sectional, descriptive study 853 children aged 6–15 years (520 boys and 333 girls) were assessed by questionnaire and clinical examinations. Caries prevalence (≥ 1 dft/DMFT) was high (91.3%). While knowledge was generally good, 83.5% boys and 85.8% girls had poor attitudes to sweet foods and > 90% frequently consumed sweet foods/beverages. Multiple regression analysis showed that children whose mothers were less educated (OR 2.46; 95% CI 1.15–5.28) and children with poor dietary attitudes and practices (OR 4.05; 95% CI 2.33–7.03 and OR 7.80; 95% CI 4.50–13.52 respectively) were more likely to have dental caries. Well-directed health promotion programmes are needed in Jazan.