This study aims to analyze managerial determinants, identify key stakeholders, and redesign managerial mechanisms for the task of horizontal integration of Chinese municipal e-government. Data were collected from a nationwide survey administered in selected municipal cities in China. Based on the Structural Equation Model, our research identified multiple managerial factors necessary for horizontal integration in e-government. These factors were Experience in general management, Reforming authority, Experience in projects, and Legal regulation. After hypothesis testing, all four determinants were found to significantly affect two intervening variables, Data integration and Business & IT integration. Furthermore, the two variables significantly predicted the dependent variable, Horizontal Integration. We then employed stakeholder analysis to find candidate stakeholders from the managerial institutions in the Chinese context, and furthermore, used a score-based approach to identify the key stakeholders corresponding to each of the above four factors. Our findings suggest that managerial mechanisms should be redesigned for a successful horizontal integration initiative.