The verdict came after an almost six-month inquest, which has cost over seven million pounds ($14 million) and has seen more than 250 witnesses from eight countries give evidence.
The couple and their driver died when their Mercedes crashed into a concrete pillar while trying to escape photographers chasing them in cars and on motorbikes. Tests conducted by French police after the accident showed that the concentration of alcohol in driver Henri Paul's blood exceeded the legal limit by several times.
The inquest to probe allegations that Diana and Dodi were murdered was first launched in 2004. It was stopped mid-way during the investigation, and resumed only in October last year after a break of nearly three years.
Mohamed al-Fayed, Dodi's father, had accused the husband of Queen Elizabeth II, Prince Phillip, of ordering the murder of his son and Diana to prevent her giving birth to Dodi's child.