Monnier was born in Paris on 26 April 1892.  Her father, Clovis Monnier (1859–1944), was a postal worker (postier ambulant), sorting mail in transit on night trains.   Her mother, Philiberte (née Sollier, 1873–1944), was "open-minded" with an interest in literature and the arts.   Adrienne's younger sister, Marie (1894–1976), would become known as a skillful embroiderer and illustrator.   Their mother encouraged the sisters to read widely from an early age and frequently took them to the theatre, opera, and ballet. 
In 1909, aged 17, Monnier graduated from high school, with a teaching qualification (brevet supérieur).
 Within months, in September, she moved to London, officially to improve her English but in reality to be close to her classmate, Suzanne Bonnierre, with whom she was "very much in love".
 Monnier spent three months working as an
Back in France, Monnier taught briefly at a private school, before enrolling on a shorthand and typing course.
 Thus equipped, in 1912, she found work as a secretary at the
Université des Annales, a
In November 1913, Monnier's father, Clovis, was seriously injured in a train crash while at work; he was left with a lifelong limp.  When the compensation came through, he gave all of it – 10,000 Francs – to Monnier, to help her set up in bookselling.