Background: The objectives were to evaluate the effectiveness of an infection control bundle in controlling the meticillin resistant Staphylococcus aureus (MRSA) transmission in residential care homes for the elderly (RCHEs) in Hong Kong. Methods:This was a two-arm cluster randomised controlled trial. Infection control bundles focused on hand hygiene (HH), environmental hygiene, and modified contact precautions were applied to the intervention arm. Nasal swabs from residents; staff HH compliance and effectiveness; and environmental hygiene were assessed by microbiological sampling or observation at the baseline and quarterly after the intervention.Results: A total of 2776 residents from 36 RCHEs were recruited. The overall MRSA prevalence was 20.4% (95% confidence interval, 18.9%-21.9%). The intervention elicited an immediate effect of 2.4% absolute decrease in the prevalence and 3.7% in the intra-facility transmission, though the difference between the two arms was insignificant. Staff HH compliance increased substantially from 5.9% to 45.6% post-intervention (p < 0.001). Conclusions:We initiated the infection control culture into the RCHEs and gained their acceptance. However, this behavioural change takes time to emerge. Our study shows that relying on the bundle alone could not bring sustainable MRSA reduction. Administrative control for strengthening infection control infrastructure is important for continuous compliance and improvement.