Background <p>Sedentary behavior (SB) is an important public health risk factor and is common among people with chronic diseases. Self-efficacy to reduce SB represents a distinct construct. Nonetheless, studies investigating interventions for SB are lacking, which may be addressed in future research. Hence, understanding the factors influencing self-efficacy to reduce SB among middle-aged and elderly people with chronic diseases holds significance.</p> Methods <p>This study included 583 middle-aged and elderly people from March 2024-May 2024 in 6 communities in Changzhou. The Chinese version of the self-efficacy to reduce sedentary behavior (SRSB) questionnaire was used to measure individuals’ confidence in reducing SB. Data were analyzed using SPSS 27.0 using descriptive statistics, cluster analysis, chi-square test, and ordered multinomial logistic regression to explore the influencing factors of SRSB in people with chronic diseases.</p> Results <p>A survey completion rate of 97.2% was achieved. A total of 583 people from 6 communities participated in this study. The median (interquartile range, IQR) score of the Chinese version of the SRSB was 3.78 (3.00–4.44), with a range of 1.0 to 5.0. Factors associated with the self-efficacy to reduce SB were body mass index (BMI), education level, number of chronic diseases, smoking status, and physical exercise.</p> Conclusions <p>The findings of this study confirmed that the self-efficacy to reduce SB of people with chronic diseases in China was at a moderate level. In health management, emphasis should be placed on overweight or obese individuals, poorly educated, having more chronic diseases, smoking, and not exercising. Health education should focus on preventive interventions against SB, promoting the adoption of beneficial lifestyles for middle-aged and elderly people with chronic diseases.</p>