Objectives: This paper aims to provide physicians with knowledge about the motivational processes surrounding exercise and diet for patients with type 2 diabetes and to offer patient support measures to favor self-management. To respond to this objective, the links between two kind of motivators (i.e., promotion and prevention foci), the Selection, Optimization and Compensation (SOC) self-management strategy, and adherence to exercise and diet of patients with type 2 diabetes were investigated for the first time in the literature. Method: A cross-sectional study was conducted with 491 French volunteer participants with type 2 diabetes diagnosed for at least 3 months (Age = 61.66 ± 9.63; BMI = 29.8 ± 5.9). Participants completed an online self-report survey measuring SOC strategy, promotion and prevention foci, and adherence to exercise and diet. Results: The main results of path and bootstrapping analysis demonstrated that promotion focus was positively related with SOC strategy (β = .69, p < .001) whereas prevention focus was not (β = −.01, ns.). On the other hand, SOC strategy was positively related with exercise (β = .20, p < .05), general diet (β = .49, p < .001), fruit and vegetable consumption (β = .27, p < .001), and spacing of carbohydrates (β = .40, p < .001), and mediated the positive link between promotion focus and these behaviors (bootstrapped 95% CI: [.11; .40], [.52; .81], [.22; .54], [.37; .70], respectively). Conclusion: This paper addresses a gap in previous research by evidencing a motivator that promotes self-management for exercise and diet among patients with type 2 diabetes. Our results suggest that physicians should privilege an interaction with patients oriented toward promotional motivation so as to favor their patients’ self-management regarding exercise and diet.