Background <p>Improving the health and well-being of Aboriginal and Torres Strait Islander Australians (hereafter referred to as Indigenous Australians) remains a national priority. While many mainstream services are already in place, Aboriginal Community Controlled Health Services (ACCHSs, hereafter referred to as Aboriginal Medical Services [AMSs]) are primarily established to provide Indigenous Australians with culturally safe, trusted, affordable, and holistic care that mainstream services often cannot offer. This study examines whether Aboriginal Medical Services/Community Centres (AMS/CC) are the usual and preferred sources of healthcare for Indigenous Australians and identifies the factors influencing these choices.</p> Methods <p>This study used data from the 2018–19 National Aboriginal and Torres Strait Islander Health Survey (NATSIHS). We analysed responses from 4,416 Indigenous adults (usual source of care) and 4,712 adults (preferred source of care). Multilevel mixed-effects logistic regression was used to examine the association between individual and contextual factors with the choice of Aboriginal Medical Services/Community Controlled Health Services (AMS/ACCHS) as the usual and preferred sources of healthcare.</p> Results <p>Our findings showed that most Indigenous Australians usually visited a mainstream GP (53%) more often than an AMS/CC (34%), while a higher proportion preferred AMS/CC (47%) over mainstream GPs (43%). The use of and preference for AMS/CC were higher among those experiencing financial stress (use: aOR = 2.25, 95% CI: 1.71–2.96; preference: aOR = 1.60, 95% CI 1.30–1.97), those satisfied with their access to cultural knowledge (use: aOR = 1.90, 95% CI: 1.38–2.61; preference: aOR = 1.40, 95% CI: 1.11–1.76), and individuals with a history of being removed from their natural family (use: aOR = 1.83, 95% CI: 1.33–2.52; preference: aOR = 1.70, 95% CI: 1.32–2.18). Experiencing discrimination in the past 12 months also increased the likelihood of using (aOR = 1.60, 95% CI: 1.20–2.13) or preferring (aOR = 1.68, 95% CI: 1.35–2.08) AMS/CC. Furthermore, Indigenous Australians living in inner or outer regional areas, very remote areas, and the Northern Territory were more likely to use or prefer AMS/CC. Conversely, those residing in less disadvantaged areas were less likely to use AMS/CC services than those in the most disadvantaged areas.</p> Conclusions <p>Since most Indigenous Australians still use mainstream GPs, this probably reflects issues with availability and access, as AMSs are not accessible everywhere, leaving people with little option other than to see a GP. The findings highlight the need to expand AMSs, especially in rural and regional areas, and to tailor mainstream healthcare to ensure services are culturally appropriate, respectful, and aligned with the values and preferences of Indigenous communities.</p>