The governor, a former emergency room doctor seeking a fourth term in office this year, told his driver to stop.
Then, according to television station KGW, Kitzhaber performed CPR on the unidentified woman, who was not breathing, and instructed a member of his security detail to call paramedics.
According to The Oregonian, the paramedics arrived two-and-a-half minutes after the call. They administered drugs and used a defibrillator to restart the woman's heartbeat.
Alan Ferschweiler, a paramedic who responded to the call, said the woman "had possibly overdosed."
"It was pretty neat to see the governor back on and going back to work,” Ferschweiler told The Oregonian. “He was surprisingly calm, and you could see he went right back to the days where he was an emergency room doctor. To go and assist the governor and take over this patient from him is pretty surprising. It definitely took us off-guard."
It's the latest situation in which Kitzhaber came to the rescue. During a gubernatorial primary debate in 2010, he ran from the stage to provide first aid to a man who was apparently suffering from a seizure.
In 2005, Kitzhaber chased down an intruder at his Portland office, eventually trapping the man in a revolving glass door.