Adverse drug events associated with anticoagulation medications are common in hospitalized patients. This study comprises a systematic review and meta-analysis of 19 trials of controlled, system-level interventions (evaluating 12,742 patients) for improving the safety or quality of anticoagulant prescribing for hospitalized adults. Due to insufficient high-quality evidence, no reviewed intervention could be recommended, although some interventions merit further evaluation such as anticoagulation consultation services and decision supported warfarin dosing. The authors conclude that additional adequately powered, controlled trials—especially of interventions designed to ensure safe prescribing of low molecular weight heparins and direct acting oral anticoagulants—are needed.