Police responded to reports of screaming at an apartment building near Locust Avenue and 20th Street around 1:20 a.m.
Upon arrival, they found a man dead "from an apparent stabbing," according to Long Beach police Sgt. Brad Johnson.
A man was caught leaving the building and detained.
The motive for the stabbing remains unknown. Long Beach police say they are not looking for any additional suspects.
Homicide detectives blocked off streets near the area.
The identity of the victim was not released pending notification of kin.
Two small children were in the residence at the time of the stabbing, and were taken into protective custody. Johnson says they will be reunited with their mother.
The relationship between the victim, children and the suspect remains unknown.
CNS contributed to this report.