AimsTo investigate the prevalence of physical inactivity in older adults living in nursing homes and explore the determinants of physical inactivity by using the Capability, Opportunity, Motivation–Behaviour model.DesignA multisite, cross‐sectional study was performed by convenience sampling and questionnaire survey.MethodsA total of 390 nursing home residents were recruited from three nursing homes in Southern China from May 2022 to April 2023. The participants completed a self‐designed general information questionnaire, Physical Activity Scale for the Elderly, Self‐Efficacy for Exercise Scale, Exercise Benefits Scale, Patient Health Questionnaire‐9 and the Short Physical Performance Battery test. Descriptive statistics, univariate analysis, Spearman correlation analysis, and ordinal logistic regression were applied for data analysis.ResultsThe prevalence of physical inactivity among the nursing home residents reached 88.46%. Ordinal logistic regression results showed that exercise self‐efficacy, perceived exercise benefits, physical function, availability of physical activity instruction, having depression, number of chronic diseases and living with spouse were the main influencing determinants of physical inactivity and explained 63.7% of the variance.ConclusionsPhysical inactivity was considerable in nursing home residents in China and influenced by complex factors. Tailored measures should be designed and implemented based on these factors to enhance physical activity while considering the uniqueness of Chinese culture.Implications for the profession and patient careHealthcare professionals should enhance physical activity of residents by increasing benefits understanding, boosting self‐efficacy, improving physical function, alleviating depression and integrating personalized physical activity guidance into routine care services. And more attention should be paid to the residents who had more chronic diseases or did not live with spouse.ImpactPhysical inactivity is a significant problem in nursing home residents. Understanding physical inactivity and its determinants enables the development of tailored interventions to enhance their physical activity level.Reporting methodThis study was reported conforming to the STROBE statement.Patients or Public ContributionNursing home residents who met the inclusion criteria were recruited.