Importance : Hand hygiene (HH) is essential to prevent hospital-acquired infections. Objective : To determine whether providing real-time feedback on a simplified HH action improves compliance with the World Health Organization’s “5 Moments” and the quality of the HH action. Design, Setting, and Participants : This open-label, cluster randomized, stepped-wedge clinical trial was conducted between June 1, 2017, and January 6, 2018 (with a follow-up in March 2018), in a geriatric hospital of the University of Geneva Hospitals, Switzerland. All 12 wards and 97 of 306 eligible health care workers (HCWs) volunteered to wear a novel electronic wearable device that delivered real-time feedback on duration of hand rubbing and application of a hand-sized customized volume of alcohol-based handrub (ABHR). Interventions : This study had 3 sequential periods: baseline (no device), transition (device monitoring without feedback), and intervention (device monitoring and feedback). The start of the transition period was randomly allocated based on a computer-generated block randomization. Main Outcomes and Measures : The primary outcome was HH compliance, according to the direct observation method during intervention as compared with baseline. Secondary outcomes included the volume of ABHR and duration of hand rubbing measured by the device during intervention as compared with transition. Results : All wards and respective HCWs were evenly assigned to group 1 (26 participants), 2 (22 participants), 3 (25 participants), or 4 (24 participants). Twelve HCWs did not fully complete the intervention but were included in the analysis. During 759 observation sessions, 6878 HH opportunities were observed. HH compliance at intervention (62.9%; 95% CI, 61.1%-64.7%) was lower than at baseline (66.6%; 95% CI, 64.8%-68.4%). After adjusting for covariates, HH compliance was not different between periods (odds ratio, 1.03; 95% CI, 0.75-1.42; P = .85). Days since study onset (OR, 0.997; 95% CI, 0.994-0.998; P < .001), older age (OR, 0.97; 95% CI, 0.95-0.99; P = .015), and workload (OR, 0.29; 95% CI, 0.20-0.41; P < .001) were independently associated with reduced HH compliance. The median (interquartile range) volume of ABHR and duration of hand rubbing in transition and intervention increased from 1.12 (0.76-1.68) mL to 1.71 (1.01-2.76) mL and from 6.5 (4.5-10.5) seconds to 8 (4.5-15.5) seconds, respectively. There were no serious adverse events. Conclusions and Relevance : The use of this device did not change HH compliance, but increased the duration of hand rubbing and volume of ABHR used by HCWs.