Besides habituation, conscious decision-making remains important for healthcare workers’ hand hygiene compliance. This study compared 307 physicians and 348 nurses in intensive care at a German university medical centre regarding their belief that hand disinfection prevents pathogen transmission. Physicians perceived less risk reduction (p < 0.001; variance explained: 4%), a comparison outscored only by lower self-rated guideline knowledge (8%). In both groups, the transmission-preventive belief was associated with high response efficacy, behavioural intention and self-efficacy, but not with self-rated knowledge. Consistent with the Health Action Process Approach, hand hygiene interventions targeting risk reduction beliefs may promote high motivation, but not action control.