: To establish the prevalence of Probable Sleep Bruxism (PSB) and its association with gender, breast or bottle-feeding, posterior and anterior crossbite, oral habits and oral breathing. : Consists of a cross-sectional study in which 151 children were submitted to a clinical oral examination for the evaluation of tooth wear, muscle discomfort and the presence of anterior and/or posterior crossbite. Parents/caregivers were asked about the frequency of teeth grinding during the child’s sleep and the occurrence of harmful oral habits, as well as the type of childbirth and breastfeeding. Data were statistically analyzed through Chi-square or Fisher’s exact tests at a 5% level of significance to determine an association among variables. : The prevalence of PSB was of 27.8% among the examined children. Among the analyzed variables, only oral breathing was statistically associated to PSB (p < 0.001), and it was verified that children with oral breathing are 2.71 times more likely to present sleep bruxism. : The prevalence of PSB in schoolchildren was high and the disorder was associated with oral breathing. Thus, pediatric dentists have an important role in the diagnosis of sleep bruxism and in monitoring breathing-related disorders.