When officers arrived to the rooming house on the 1400 block of West Allegheny Avenue, they found two people with multiple stab wounds.
A woman in her 40s was stabbed nine times and a man in his 60s was stabbed 16 times, police said.
Both were taken to an area hospital, where the woman was listed in critical condition and the man was listed in stable condition.
Police said the man is being held as a suspect.
No additional information was immediately available.