Alboni was born at Città di Castello, in Umbria. She became a pupil of of Cesena, Emilia–Romagna, and later of the composer Gioachino Rossini, when he was 'perpetual honorary adviser' in (and then the principal of) the Liceo Musicale, now Conservatorio Giovanni Battista Martini, in Bologna. Rossini tested the humble thirteen-year-old girl himself, had her admitted to the school with special treatment, and even procured her an early engagement to tour his "Stabat Mater" around Northern Italy, so that she could pay for her studies. After she achieved her diploma and made a modest debut in Bologna, in 1842, as "Climene" in Pacini's "Saffo", she obtained a triennial engagement thanks to Rossini's influence on the impresario Bartolomeo Merelli, Intendant at both Milan's Teatro alla Scala and Vienna's Imperial Kärntnertortheater. The favourable contract was signed by Rossini himself, "on behalf of Eustachio Alboni", father of Marietta, who was still a minor. The singer remained, throughout her life, deeply grateful to her ancient "maestro", nearly a second father to her.