Physical activity has cultural significance and population health benefits. However, Aboriginal and Torres Strait Islander adults may experience challenges in participating in physical activity. This mixed methods systematic review aimed to synthetize existing evidence on facilitators and barriers for physical activity participation experienced by Aboriginal and Torres Strait Islander adults in Australia. The Joanna Briggs Institute methodology was used. A systematic search was undertaken of 11 databases and 14 grey literature websites during 2020. The included studies reported physical activity facilitators and barriers experienced by Aboriginal or Torres Strait Islander participants aged 18+ years, living in the community. Twenty-seven studies met the inclusion criteria. Sixty-two facilitators were identified: 23 individual, 18 interpersonal, 8 community/environmental and 13 policy/program facilitators. Additionally, 63 barriers were identified: 21 individual, 17 interpersonal, 15 community/environmental and 10 policy/program barriers. Prominent facilitators included support from family, friends, and program staff, and opportunities to connect with community or culture. Prominent barriers included a lack of transport, financial constraints, lack of time, and competing work, family or cultural commitments. Aboriginal and Torres Strait Islander adults experience multiple facilitators and barriers to physical activity participation. Strategies to increase participation should seek to enhance facilitators and address barriers, collaboratively with communities, with consideration to the local context.