Background: Participation in sport and physical activity (PA) leads to better overall health, increased life expectancy, and decreased mortality rates across the lifespan; however, there may be a range of individual, family, and community factors that influence PA participation among ONENA children and adolescents residing in the 22 Pacific Island Countries and Territories (PICT) and Australia. This review aimed to synthesise existing quantitative and qualitative literature regarding barriers to and facilitators of PA and sport among ONENA youth. Methods: The literature was systematically searched to include studies reporting barriers to and facilitators of PA and sports participation among ONENA children and adolescents aged 0–18 years residing in the 22 PICT and Australia. Using a pre-established taxonomy based on the social-ecological model, a deductive analysis was performed. Quality appraisal was performed using the mixed methods appraisal tool. Results: Of 1388 articles, 14 studies were included, with 128 ONENA children and adolescent participants across the four qualitative studies; 156,581 ONENA children and adolescents across the seven quantitative studies; 801 parents, children, and adolescents in one quantitative study; and 642 parents in two quantitative studies. Of the 14 included studies, none were based in Australia and only 10 of the 22 PICT were reported as the participants’ residence: Palau, New Zealand, Tonga, Cook Islands, Kiribati, Samoa, Solomon Islands, Tuvalu, Vanuatu, and Fiji. Four studies reported barriers, and another four studies reported facilitators of PA and sport, with the remaining studies reporting both barriers and facilitators. Overall, there were more barriers reported (30 in total) than facilitators (27 in total). Conclusions: Research in this area is lacking, with ONENA youth living in Australia and 12 PICT not represented. Overall, there were a larger number of facilitators experienced at individual and interpersonal levels, while barriers were highest at the community level, with the policy level having facilitators and barriers equally represented. Programs that offer PA and sport participation options with embedded SDT-informed strategies for all family members; that are accessible through existing transport and related social, cultural, and physical infrastructure; and that are committed to communities through formal co-design partnerships are needed, to enhance the PA and sport participation of ONENA youth residing in PICT.