Health Inspectorate Wales said Wrexham Maelor Hospital staff were under "considerable pressure" for long periods as ambulances waited outside.
It said inspectors were told the situation was not unusual.
Betsi Cadwaladr University Health Board said it was working to manage the pressures.
Inspectors visited the A&E unit and another ward on 30 September and 1 October last year and have released reports about what they found.
Despite the pressures in A&E they said staff were observed to be effectively prioritising clinical need and patient care.
On the Mason Ward, inspectors found patients to be well looked after and said staff were committed to providing good standards of care.
Angela Hopkins, executive director of nursing and midwifery at the health board, said its hospitals were experiencing growing demand like the rest of the UK.
"We are focussing on the improvement of emergency department and ward processes for both admission and discharge to reduce delays," she said.
"We are increasing the numbers of nursing staff and extra beds have been opened.
"We are also working in partnership with local authorities and the Welsh Ambulance Service to ensure that the system works more smoothly to improve patient flow through the hospital."
An unannounced inspection of an under-pressure A&E unit at a north Wales hospital led to concerns for patient safety, a watchdog says.