A 20-year-old man has been stabbed in the leg in Sydney's northwest and police are appealing to the public to help find his attackers.

The man was standing with a group of people on a footpath in Ermington on Saturday night when two men and three women approached and attacked him, police say.

The 20-year-old was stabbed in the leg. (9NEWS)

The man was standing with a group of people on the footpath when the attack occurred. (9NEWS)

Police at the scene in Ermington. (9NEWS)

He was taken to hospital with non-life-threatening injuries.

His alleged attackers are said to be in their early 20s and of Asian appearance.

© AAP 2016