Emergency services were called at roughly 2pm to the incident.
The casualty was taken by air to Ysbyty Gwynedd, Bangor.
A Welsh Ambulance Service spokesperson said: “We were called on Tuesday (August 29), at approximately 2.01pm, to reports of an incident at a property in Holyhead.
“We sent one emergency ambulance and one air ambulance to the scene where we were assisted by colleagues from the Emergency Medical Retrieval and Transfer Service who travelled by air.
“We conveyed one patient by air to Ysbyty Gwynedd, Bangor for further treatment.”