ObjectiveTo investigate the determinants of willingness and practice of physicians’ online medical services (OMS) uptake based on social ecosystem theory, so as to formulate OMS development strategies.DesignCross-sectional survey.SettingResearch was conducted in two comprehensive hospitals and two community hospitals in Jiangsu, China, and the data were gathered from 1 June to 31 June 2020.ParticipantsWith multistage sampling, 707 physicians were enrolled in this study.Outcome measureDescriptive statistics were reported for the basic characteristics. χ2 test, Mann-Whitney U test and Spearman’s correlation analysis were used to perform univariate analysis. Linear regression and logistic regression were employed to examine the determinants of physicians’ OMS uptake willingness and actual uptake, respectively.ResultsThe mean score of the physicians’ OMS uptake willingness was 17.33 (range 5–25), with an SD of 4.39, and 53.3% of them reported having conducted OMS. In the micro system, factors positively associated with willingness included holding administrative positions (b=1.03, p<0.05), OMS-related awareness (b=1.32, p<0.001) and OMS-related skills (b=4.88, p<0.001); the determinants of actual uptake included holding administrative positions (OR=2.89, 95% CI 1.59 to 5.28, p<0.01), OMS-related awareness (OR=1.90, 95% CI 1.22 to 2.96, p<0.01), OMS-related skills (OR=2.25, 95% CI 1.35 to 3.74, p<0.01) and working years (OR=2.44, 95% CI 1.66 to 3.59, p<0.001). In the meso system, the hospital’s incentive mechanisms (b=0.78, p<0.05) were correlated with willingness; hospital advocated for OMS (OR=2.34, 95% CI 1.21 to 4.52, p<0.05), colleagues’ experiences (OR=3.81, 95% CI 2.25 to 6.45, p<0.001) and patients’ consultations (OR=2.93, 95% CI 2.02 to 4.25, p<0.001) were determinants of actual uptake. In the macro system, laws and policies were correlated with willingness (b=0.73, p<0.05) and actual uptake (OR=1.98, 95% CI 1.31 to 2.99, p<0.01); media orientation was also associated with willingness (b=0.74, p<0.05).ConclusionMultiple determinants influence physicians’ OMS application. Comprehensive OMS promotion strategies should be put forward from multidimensional perspectives including the micro, meso and macro levels.