A woman has been arrested after a health employee was stabbed in the neck near Royal Prince Alfred Hospital in Sydney's inner west on Monday morning.

The attack took place outside the McDonald's cafe on Missenden Road, Camperdown, shortly before 11.30am.

The 34-year-old victim was taken to Royal Prince Alfred Hospital, where police said she will undergo surgery.

She's currently in a serious but stable condition.

According to Seven News, the alleged attacker was a mental health patient the victim was being counselled by.