Method of preparing an edible oil, characterized by an increased shelf-life, and edible oil obtainable by such method is provided. A method of preparing an edible oil, particularly extra virgin olive oil, is described, including the operation of introducing a predetermined number of olives having a polyphenolic content ranging between 1000-3000 mg of polyphenols/kg of olives in a predetermined volume of oil. In a preferred embodiment, the olives are preventively treated with an anti-mould agent, and are dehydrated, preferably by thermal treatment in an oven at a temperature ranging between 80° C. and 160° C., so as to achieve the elimination of a water amount ranging between 1% and 30%, preferably between 7% and 15%, more preferably of about 10%. The method of the invention allows obtaining an edible oil, particularly extra virgin olive oil, having an increased polyphenolic content, thereby an increased shelf-life, while maintaining the organoleptic characteristics unaltered.