Delacherois-Day joined the advertising department at the magazine 10 years ago but moved abroad in 2007.
She returned to Vogue in September 2013, and became the ad manager in December that year. Delacherois-Day handles the British fashion category, several London media agencies and manages Miss Vogue, the title aimed at a younger audience.
The move follows a good year for Vogue which will post an extra 17 pages of ads, year on year, in 2014 to 1,889. It published the largest ever fashion issue for its September edition at 460 pages, which carried £4.5 million worth of ads.
Stephen Quinn, the publishing director at Vogue, said: "Lucy is ready for a senior management role and will be a singular asset to Vogue as we storm ahead to the centenary."