Introduction: Dental caries in children is a multifactorial and complex condition. Toothbrushing helps maintain good oral hygiene and delivers fluoride. However, determinants of toothbrushing could vary based on Indigenous status. Objective: This study aimed to assess the association between socioeconomic status and adequate toothbrushing practice (brushing twice or more a day) in Indigenous and non-Indigenous Australian children. Methods: Data were acquired from the National Child Oral Health Survey (NCOHS) 2012 to 2014. NCOHS administered questionnaires to parents of a representative sample of 24,215 Australian children aged 5 to 14 y recruited using a complex sampling method. Data on the frequency of toothbrushing and socioeconomic status were collected through the questionnaires. Statistical analysis was conducted progressively from bivariate to multivariable regression modeling, stratified by Indigenous status. Results: Just over half of Indigenous children and over two-thirds of non-Indigenous children reported adequate toothbrushing. The prevalence of adequate brushing (twice or more a day) was 42% (95% confidence interval [CI], 1.10–1.84) higher among children with an overseas-born parent than those with Australian-born parents. Among non-Indigenous children, sex and age, parents’ country of birth, number of children in the family, and other family socioeconomic indicators (education, income, private health insurance) were associated with adequate toothbrushing. The prevalence of adequate brushing was 1.09 (95% CI, 1.03–1.15) and 1.15 (95% CI, 1.10–1.21) times higher when their parent possessed vocational training and tertiary education, respectively, compared to those children whose parents had school-level education. Conclusions: There were differences in patterns of socioeconomic disparities for toothbrushing practices between Indigenous and non-Indigenous Australian children. Knowledge Transfer Statement: To promote positive toothbrushing practices in children, dental clinicians and public health professionals must be aware of the determinants of toothbrushing practices. Socioeconomic disparities in toothbrushing frequency were more apparent in non-Indigenous children. These results will help develop population-specific interventions that tackle the determinants to help improve oral hygiene behavior in Indigenous and non-Indigenous children.