Although the process-based model of policing has been widely tested, research on how procedural justice works within police agencies, particularly its impact on officer willingness to engage in procedurally fair behavior on the street, is relatively scant. Based on survey data collected from Chinese police officers, this study assessed the linkages between internal procedural justice and external procedural justice through the mechanisms of moral alignment with both supervisors and citizens and perceived citizen trustworthiness. Greater internal procedural justice was directly related to higher external procedural justice. Fair supervision helped build up moral alignment between officers and supervisors and between officers and citizens, which in turn led to stronger commitment to fair treatment of the public. Internal procedural justice and moral alignment with citizens also cultivated officers’ perceptions of public trustworthiness, which further strengthened officers’ fair treatment toward the public.