Objective: To investigate the self-care activities and their influencing factors among young and middle-aged patients with type 2 diabetes mellitus ( T2DM ), so as to provide the basis for the care management of T2DM. Methods: T2DM patients at ages of 18 to 59 years that were admitted to Department of Endocrinology, Hangzhou First People's Hospital Affiliated to Medical School of Zhejiang University were selected using the convenient sampling method from January to August 2021, and the demographic data were collected using questionnaires, including gender, age and educational levels. The self-care level was measured using the Summary of Diabetes Self-Care Activities ( SDSCA ) was used to assess self-management behaviors, and the social support level was evaluated using the Social Support Rating Scale ( SSRS ), while the coping modes were assessed using the Medical Coping Modes Questionnaire ( MCMQ ). Factors affecting the self-care activities were identified among young and middle-aged patients with T2DM using multivariable linear regression analysis. Results: The 342 respondents included 185 men ( 54.07% ) and 157 women (45.93% ), and had a mean age of ( 43.76±3.82 ) years. The total score of self-care activities was ( 94.22±18.74 ), and the overall scoring rate was 72.48%, including 63 cases with high scores ( 18.42% ), 208 cases with moderate scores ( 60.82% ) and 71 cases with low scores ( 20.76% ). Multivariable linear regression analysis identified gender ( women, β'=0.213 ), educational level ( high school/technical secondary school, β'=0.187; diploma and above, β'=0.411 ), household monthly income per capita (5 000 Yuan and higher, β'=0.390), course of disease ( >5 years, β'=0.340 ), history of receiving health education targeting diabetes ( β'=0.411 ), coping mode ( avoidance, β'=0.195; confronce, β'=0.367 ) and social support level ( general, β'=0.206; high, β'=0.383 ) as factors affecting self-care activities among young and middle-aged patients with T2DM. Conclusions The overall self-care activities at a moderate level among young and middle-aged patients with T2DM, which are associated with gender, educational level, economic income, course of disease, health education targeting diabetes, coping mode and social support level.