One passenger, a woman in her 20s, was pronounced dead at the scene following the 1:13 a.m. solo-vehicle collision, police said.
The male driver and a child who was also in the car remain hospitalized this afternoon with what police described as serious injuries.
The car, a Cadillac, appears to have been traveling north on California Street when it struck a roundabout at Allston Way, then hit a tree on the east side of California just north of Allston, according to police.
Police said they are investigating the cause of the collision, including the possibility that the driver was impaired.
The roundabout is intended to be a traffic-calming feature. While there have been collisions at such features in the past, police said in a statement that "the number is not remarkable enough to suggest that they are a significant issue in this collision."
This is the second fatal collision in Berkeley this year.
Tyler DeMartini, 18, was struck by a car at Marin and Tulare avenues in North Berkeley on Jan. 20 as he was riding his skateboard home and later died of his injuries.
The driver who hit him, a 54-year-old Berkeley man, cooperated with police and was not intoxicated, according to police.