It happened just after midnight on Friday in a house on the 1700 block of North Stillman Street in the Strawberry Mansion section of Philadelphia.
Police say the victim, a 41-year-old woman, was fighting with a 51-year-old woman in some sort of romantic dispute over a man.
According to investigators the women were fighting in front of the home when the suspect went inside, got the hammer, and attacked the victim.
The younger woman was taken to Hahnemann University Hospital where she was pronounced dead shortly after 1:00 a.m.
The identities of those involved have not been released.
