Objective: The purpose of this study is to understand the current situation of knowledge, attitude, and practice of self-management in young patients with type 2 diabetes mellitus (T2DM) and to explore the relationship between general conditions (personal, social, and environment, clinical factors) and their knowledge, attitude, and practices (KAP) of diabetes self-management, This aims to provide patients with high-quality nursing care management and services, as well as to provide relevant recommendations for effective self-management. Methods: This study is a descriptive correlational study that used the purposive sampling method to investigate 359 patients with T2DM aged 18–25 years in four designated tertiary hospitals in Shandong Province. Results: Knowledge of self-management was correlated with sex, age, education level, occupation and work situation, monthly household income, medical payment method, family and friend support, frequency of diabetes health education, and diabetes complications. The attitude subscale was correlated with sex, age, education level, work situation, and family and friend support. The practice subscale was associated with age, education level, work situation, family and friend support, frequency of diabetes health education, and HbA1c values. Conclusion: Young adults aged 18–25 with T2DM have positive attitudes towards diabetes self-management, but there are still deficiencies in knowledge acquisition and behavioral practice. The KAP of self-management of diabetes is influenced by personal factors such as sex, age, and education level, and socio-environmental factors such as family income and family or friends’ social support. Additionally, clinical factors such as complications and HbA1c values significantly impacted the patient’s disease self-management ability.