The crash happened at about 10 p.m. Tuesday night near the intersection of San Gabriel Boulevard and East Grand Avenue.
Police said a Range Rover driving southbound crossed into northbound lanes and hit a Honda head on.
The driver of the Honda was rushed to the hospital and listed in critical condition.
No one else was seriously injured.
Police arrested the driver of the range rover, 22-year-old Kai Tien of Rosemead.
He was booked for driving under the influence with bodily injury.