This study aimed to investigate whether an ongoing, iterative approach of information, training, observation, and feedback could improve hand hygiene compliance in healthcare professionals. Direct observation by hygiene experts was used to measure compliance rates. Between 2013 and 2017, 6,009 healthcare professionals were trained, and compliance measurements were performed in 49 wards. Overall 19,295 opportunities for hand hygiene were observed. The results showed an increase in the overall mean hand hygiene compliance rate from 81.9% in 2013 to 94% in 2017. Physicians' hand hygiene compliance increased from 69.0% to 89.3% and the compliance of nurses increased from 86.0% to 96.4%. The compliance rates for all healthcare professional groups and all "My five moments for hand hygiene" also increased over the study period. Therefore, an iterative approach of information and training paired with feedback can be successful in improving hand hygiene compliance rates among healthcare professionals.