It happened around 2:41 p.m. Wednesday on the 5400 block of Chestnut Street in West Philadelphia.
Police say a 55-year-old man was stabbed twice in the chest, and one time in the forearm, neck and cheek.
The victim was rushed to an area hospital where he was placed in critical condition.
There was no immediate word on what sparked the stabbing.
No arrests have been made.
Anyone with any information is asked to call police at 215-686-TIPS.