Officers were called to the A27 Mansbridge Road last Thursday after a collision involving a pedestrian and an orange, trail-style motorbike and a pedestrian.
The pedestrian has been named as Adam Wilcox, 55, of Colehill Crescent in Bournemouth.
He taken to Southampton General Hospital with life-threatening injuries and died the following day.
His next of kin have been informed and are being supported by specialist officers.
Police are continuing to investigate the exact circumstances of the collision, which took place near the White Swan pub at around 7.40am.
The road was shut in both directions following the crash and remained closed for three hours.
Speaking at the time, a spokesperson for South Central Ambulance Service said: “We sent an ambulance, a paramedic team leader in a rapid response vehicle and the Hampshire & Isle of Wight Air Ambulance critical care car to the incident.
“The pedestrian was a 55-year-old male who had sustained serious head injuries and was in a life-threatening condition.
“After initial treatment at the scene he was then taken to hospital.
Anyone with information, including dash cam footage, can call Hampshire police 101, quoting reference number 44190080297. Alternatively they can call Crimestoppers on 0800 555 111.