Cwm Taf health board has tweeted to advise patients that A&E services at Royal Glamorgan are under pressure.
It has asked those with minor injuries to visit Ysbyty Cwm Rhondda instead, which is just under 10 miles away.
Royal Glamorgan Hospital A&E is very busy today. If you have a minor injury please call 01443 444 075 for appointment at Ysbyty Cwm Rhondda
It comes ahead of a debate by Assembly Members later on how to prepare the Welsh NHS for another busy winter.