Background: Adolescents with T2D engage in little moderate-to-vigorous PA. Although autonomous (internally driven) motivation is associated with PA engagement in healthy individuals, whether this is true for AYA with T2D or prediabetes is unknown. Methods: Participants were 13-22 years old with T2D or prediabetes who were enrolled in an ongoing trial (NCT04874415) to promote PA. Prior to randomization, we assessed autonomous motivation to exercise (Relative Autonomy Index, RAI) using the Behavioral Regulation to Exercise Questionnaire-3. To assess PA, AYA completed PACE+ survey (days active <60 min in last and typical weeks) and used a wrist-worn activity tracker for 14 days. Associations between RAI and PA were assessed using Pearson correlation and linear regression. Results: Participants (n=33; 19F; 19 T2D, 14 prediabetes) were 15.9 ± 2.0 years and racially diverse (57% non-White). Correlation between RAI and step count was strong (r=0.5, p=0.001), and the highest RAI quartiles achieved <3000 more steps/day than the lowest (p<0.05). RAI also correlated with PACE+ days active/week (r=0.4, p=0.01). Relationships persisted after adjustment for age, sex, race, and T2D. Conclusion: Greater autonomous motivation to exercise was associated with higher objective and subjective PA. Autonomous motivation may be a target for behavioral intervention in AYA with T2D or prediabetes. Disclosure M.Vajravelu: None. A.Rodriguez gonzalez: None. B.Hewitt: None. A.Kriska: None. J.Mitchell: None. V.Helgeson: None. S.Amaral: Advisory Panel; Bristol-Myers Squibb Company. S.A.Arslanian: Advisory Panel; Novo Nordisk, Eli Lilly and Company, Consultant; Société des Produits Nestlé SA,, Other Relationship; Eli Lilly and Company, AstraZeneca, Research Support; Novo Nordisk, Eli Lilly and Company. Funding National Institutes of Health (K23DK125719, UL1TR001857)