Protected mealtimes is an initiative to support increased nutritional intake for all hospitalised patients, particularly those who are malnourished. This prospective, stepped wedge cluster randomised controlled trial was undertaken at three hospital sites in Melbourne, Australia. Implementation science principles and the British Hospital Caterers Association reference policy on Protected Mealtimes guided the intervention. Primary outcomes were daily energy and protein intake. There were 149 unique participants, with 416 observations of 24-hour food intake. Energy and protein intakes were not significantly different between the intervention and control periods. Implementation fidelity was variable across individual aspects of the Protected Mealtimes policy. This trial utilised high quality methods with results supporting the non-significant findings of previous observational studies of Protected Mealtimes. As such, we encourage the consideration of other evidence-based approaches to support nutritional intake of hospitalised patients.