Objectives: To synthesize the literature describing interventions to improve hand hygiene in ICUs, to evaluate the quality of the extant research, and to outline the type, and efficacy, of interventions described.Data Sources: Systematic searches were conducted in November 2016 using five electronic databases: Medline, CINAHL, PsycInfo, Embase, and Web of Science. Additionally, the reference lists of included studies and existing review papers were screened.Study Selection: English language, peer-reviewed studies that evaluated an intervention to improve hand hygiene in an adult ICU setting, and reported hand hygiene compliance rates collected via observation, were included.Data Extraction: Data were extracted on the setting, participant characteristics, experimental design, hand hygiene measurement, intervention characteristics, and outcomes. Interventional components were categorized using the Behavior Change Wheel. Methodological quality was examined using the Downs and Black Checklist.Data Synthesis: Thirty-eight studies were included. The methodological quality of studies was poor, with studies scoring a mean of 8.6 of 24 (sd = 2.7). Over 90% of studies implemented a bundled intervention. The most frequently employed interventional strategies were education (78.9%), enablement (71.1%), training (68.4%), environmental restructuring (65.8%), and persuasion (65.8%). Intervention outcomes were variable, with a mean relative percentage change of 94.7% (sd = 195.7; range, 4.3-1155.4%) from pre to post intervention.Conclusions: This review demonstrates that best practice for improving hand hygiene in ICUs remains unestablished. Future research employing rigorous experimental designs, careful statistical analysis, and clearly described interventions is important.