**Background:** Hand hygiene is essential for infection prevention. This study aimed to find a suitable theoretical model and identify critical facilitators and barriers to explain hospital visitors’ hand hygiene practice.
**Methods:** Visitors in four hospitals were observed and asked to give explanations for using or not using the hand rub dispenser. The written explanations of N = 838 participants were coded according to three theoretical models: Theory of Planned Behavior (TPB), Health Action Process Approach (HAPA), and Theoretical Domains Framework (TDF).
**Results:** Self-reported hand hygiene behavior differed from observed behavior, with 15.75% wrongly claiming to have cleaned their hands. Critical facilitators for hand hygiene were attitude towards the behavior; subjective norm; outcome expectancies; risk perception; planning; action control; knowledge and skills; motivation and goals; and social influences. Key barriers included perceived behavioral control; barriers and resources; memory, attention, and decision processes; and environmental context and resources.
**Conclusions:** Visitors’ self-reported hand hygiene behavior is overreported. Both HAPA and TDF were identified as suitable theoretical models for explaining visitor’s hand hygiene practice. Future behavior change interventions should focus on 1) visibility and accessibility of cleaning products; 2) informing laypeople about their role regarding infection prevention; and 3) leveraging social influence processes.
