On September 30, 1955, Dean and his mechanic Rolf Wütherich set off from Competition Motors, where they had prepared his Porsche 550 Spyder that morning for a sports car race atSalinas, California. Dean originally intended to trailer the Porsche to the meeting point at Salinas, behind his new Ford Country Squire station wagon, crewed by Hickman and photographer Sanford Roth, who was planning a photo story of Dean at the races. At the last minute, Dean drove the Spyder, having decided he needed more time to familiarize himself with the car. At 3:30 p.m., Dean was ticketed in Mettler Station, Kern County, for driving 65 mph (105 km/h) in a 55 mph (89 km/h) zone. The driver of the Ford was ticketed for driving 20 mph (32 km/h) over the limit, as the speed limit for all vehicles towing a trailer was 45 mph (72 km/h). Later, having left the Ford far behind, they stopped at Blackwells Corner in Lost Hills for fuel and met up with fellow racer Lance Reventlow.
Dean was driving west on U.S. Route 466 (later State Route 46) near Cholame, California when a black-and-white 1950 Ford Custom Tudor coupe, driven from the opposite direction by 23-year-old Cal Poly student Donald Turnupseed, attempted to take the fork onto State Route 41 and crossed into Dean's lane without seeing him. The two cars hit almost head on. According to a story in the October 1, 2005 edition of the Los Angeles Times, California Highway Patrol officer Ron Nelson and his partner had been finishing a coffee break in Paso Robles when they were called to the scene of the accident, where they saw an unconscious but heavily breathing Dean being placed into an ambulance. Wütherich had been thrown from the car, but survived with a broken jaw and other injuries. Dean was taken to Paso Robles War Memorial Hospital, where he was pronounced dead on arrival at 5:59 p.m. by the attending emergency room physician. His last known words, uttered right before impact, were said to have been: "That guy's gotta stop... He'll see us."
According to the postmortem report, it is believed that Dean's head impacted with the front grill of the other car. This impact and the accompanying crash resulted in Dean suffering a broken neck, plus multiple fractures of the jaw, arms and legs, as well as massive internal injuries. He is believed to have died around ten minutes after the crash upon examination in the ambulance. For years, there were rumors a photographer friend, traveling to the race in another car, took photos of Dean trapped in the car dead or dying. Such photos never surfaced in public.
Contrary to reports of Dean's speeding, which persisted decades after his death, Nelson said "the wreckage and the position of Dean's body indicated his speed was more like 55 mph (88 km/h)." Turnupseed received a gashed forehead and bruised nose and was not cited by police for the accident. He was interviewed by the Tulare Advance-Register newspaper immediately following the crash, saying that he had not seen Dean's car approaching, but after that, refused to ever again speak publicly about the accident. He went on to own and operate an electrical contracting business and died of lung cancer in 1995. Wütherich died in a road accident in Germany in 1981 after surviving several suicide attempts.
While completing Giant, and to promote Rebel Without a Cause, Dean filmed a short interview with actor Gig Young for an episode of Warner Bros. Presents in which Dean, instead of saying the popular phrase "The life you save may be your own" instead ad-libbed "The life you might save might be mine." [sic] Dean's sudden death prompted the studio to re-film the section, and the piece was never aired-though in the past several sources have referred to the footage, mistakenly identifying it as a public service announcement. (The segment can, however, be viewed on both the 2001 VHS and 2005 DVD editions of Rebel Without a Cause).