The Healthcare Environment Inspectorate (HEI) said there are “several areas for improvement” in ward four.
The hospital, which has beds for 132 patients, is due to be replaced by a new facility next September, which is being built beside the Royal Infirmary of Edinburgh.
The HEI report said across the hospital “generally, we saw good staff compliance with hand hygiene”.
But in ward four, which deals with orthopaedic and gastrointestinal patients, inspectors noted “some instances of poor compliance with hand hygiene”.
The report said: “Staff did not always take the opportunity to perform hand hygiene and, on several occasions, alcohol-based hand rub was applied but the technique to decontaminate hands was poor. We also saw some examples of staff not removing their aprons and gloves or not decontaminating their hands on removal.”
Inspectors also said they saw staff using monitoring equipment on several patients throughout the day “without appropriate decontamination (cleaning) of the equipment taking place between patients”.
HEI has now said NHS Lothian “must ensure compliance with infection prevention and control policies”.
Inspectors also found that in ward one, where children with respiratory and other problems are treated, three of the four mattresses they checked had “visible contamination on the inside of the mattress covers”.
Jacqui Macrae, head of quality of care for Healthcare Improvement Scotland, said: “In this inspection we found that the wards and departments were generally clean, however we have also identified a number of areas that need to be addressed.
“NHS Lothian must ensure compliance with infection prevention and control policies, implement improvement action plans and ensure all equipment used in the care environment is clean.
“This inspection resulted in five requirements and two recommendations which we expect NHS Lothian to address as a matter of priority. We will continue to inspect the Royal Hospital for Sick Children to ensure improvements are made.”
Dr David Farquharson, medical director at NHS Lothian, said: “We welcome the report from the Healthcare Environment Inspectorate and we are pleased that some areas were singled out for individual praise, including the cleanliness of the hospital and that overall staff are working hard to comply with standard infection control precautions.
“We recognise there are things that can be improved and they will be addressed as a matter of urgency. These include reinforcing general infection control measures with staff, better documentation surrounding vascular catheters and improve the checking and cleaning of all equipment including mattresses.”