Objective Guided by the Information-Motivation-Behavioral Skills Model, this study aims to explore the path of delay discounting and self-regulatory fatigue on the relationship between diabetes knowledge and self-management behavior in patients with diabetes mellitus (DM). Methods A convenience sample of 310 DM patients was surveyed using the Summary of Diabetes Self-Care Activities, the Self-Regulatory Fatigue Scale, the Quick Delay Questionnaire, and the Audit of Diabetes Knowledge. Structural equation model was used to analyze the effect path. Results The mean score for self-management behavior in DM patients was (44.95±16.01). Mediation analysis revealed a chain mediating effect of delay discounting and self-regulatory fatigue on the relationship between diabetes knowledge and self-management behavior, accounting for 13.93% of the total effect. Conclusion Delay discounting and self-regulatory fatigue impede the translation of disease knowledge into healthy behavior. Beyond health education, medical staff should address these underlying psychological factors to improve self-management behavior of patients.