The stabbing happened around 1:25 p.m. in the 9100 block of South Commercial Avenue, Chicago police said.
Chopper 7 was over the scene, where Chicago police could be seen. It was not immediately clear if the stabbing happened inside or outside of the Walgreen's.
A 35-year-old man was stabbed in his shoulder by a knife after he was in a verbal altercation with the offender, which turned physical, police said.
The victim was taken to a hospital in good condition.
"We are aware and are cooperating with CPD in their investigation. The safety of everyone in out stores is our priority," a Walgreen's spokesperson said in a statement.
The offender fled the scene in a silver Dodge minivan, police said.
No arrests have been made. Chicago police continue to investigate.