Officers responded just after 9:35 a.m. to the 1000 block of Pacific Avenue, near St. Mary Medical Center, on reports of the stabbing, according to the Long Beach Police Department.
The first arriving officer made contact with a witness who pointed out the man, who matched the description of the suspected stabber, and he was taken into custody.
Additional officers searched the area and found a roughly 50-year-old woman unresponsive inside an apartment, according to police.
Paramedics were called to the scene and took the woman to a hospital, where she was pronounced dead. Her name was not immediately released.
A preliminary investigation into the stabbing established the suspect and the woman were mother and son, and detectives learned the man allegedly stabbed his mother several times in her upper body following an argument that escalated.
No one else was in the apartment during the stabbing, and no other injuries were reported, according to police.
The man was waiting booking charges pending completion of the investigation into the stabbing. His name was not released.