A police sergeant on patrol discovered the crash, which caused extensive property damage, at about 2:05 a.m. near 6th Avenue and Union Street.
Medics responded and found one male passenger, believed to be in his late 20s or early 30s, dead at the scene, said Detective Jeff Kappel of the Seattle Police Department.
The driver and the other passenger were both transported to Harborview Medical Center with non-life-threatening injuries.
A preliminary investigation found that the three men were heading south on Interstate 5 in a BMW 745 sedan when the driver lost control as he attempted to negotiate the Union Street exit.
The car slammed into a concrete barrier and a wall, overturned and came to rest a short distance east of 6th Avenue and Union Street.
The driver, a 31-year-old man, was under police guard at the hospital and was booked into the King County Jail for investigation of vehicular homicide when he was released Saturday afternoon, Kappel said.
Traffic collision investigation squad detectives responded to the scene and continue to actively investigate.