Background: Early childhood caries disproportionately affects vulnerable groups and remains a leading cause of preventable hospital admissions for Western Australian children. The Western Australia State Oral Health Plan seeks to improve child oral health through universal and targeted health promotion initiatives with primary caregivers. These initiatives require evidence of primary caregiver oral health knowledge and behaviours and baseline data on early childhood caries. The objective of this systematic scoping review was to understand current oral health knowledge and practices of primary caregivers of children aged 0–4 years, identify influential socioecological determinants, and identify data on early childhood caries in the Western Australian context. Methods: A systematic scoping review framework identified articles published between 2010 and 2021, using Scopus, PubMed, Medline, CINAHL, PsycINFO, selected article reference lists, and oral health websites. The lack of Western Australian specific literature prompted the inclusion of Australia-wide articles. Articles were screened via author consensus, with eight selected. Results: Western Australia and nation-wide data on early childhood caries are limited and mostly dated. WA data from children aged 2–3 years, collected in 2006, suggests the prevalence is 2.9% in this state, with national data of children from 0 to 3 years, collected from 2006 and 2008, suggesting an early childhood caries prevalence of 3.4–8% of children aged 18 months, rising sharply by 36 months of age. Nationally, fewer than half the primary caregivers reported following evidence-based oral health recommendations for their young children. Perceptions of the role of dental services for young children tends to be focussed on treatment, rather than surveillance and prevention. Knowledge of dietary and oral hygiene practices is inconsistent and awareness of the Child Dental Benefit Schedule low. Young children’s oral health status is clearly associated with socioecological factors, including socioeconomic status. Conclusions: Recent early childhood caries data and evidence of primary care-givers’ oral health knowledge and behaviours are unavailable in Western Australia, a similar situation exists nationwide. To realise the Western Australian and National Oral Health Plans, research is required to address this knowledge gap.