Josephine Éva Phoebe Gauthier was born on September 20, 1885 in Ottawa, Ontario. There Éva took piano, harmony and voice lessons, and sang at St. Patrick's Church and Ottawa's Notre Dame Basilica. In those days, Canadian musicians normally sought training under European teachers, so Gauthier travelled to Europe in 1902, at age 17, with the assistance of her uncle and aunt, Sir Wilfrid Laurier and Lady Zoë Laurier. In France, Gauthier studied voice privately with Auguste-Jean Dubulle of the Paris Conservatory, and underwent surgery to correct nodules on the vocal cords. Subsequently, she studied with Jacques Bouhy, whom she credited for her vocal technique.
In Europe, Gauthier learned the standard vocal repertoire. Originally she performed as a contralto, but she expanded her range to include the soprano and even coloratura registers, though she became known primarily as a mezzo. Throughout her career, she used her wide vocal range to advantage.
By 1905, Gauthier had been engaged by the pre-eminent Canadian singer Dame Emma Albani for a concert tour of the United Kingdom and for Albani's 1906 Canadian farewell tour. Gauthier was paid $70 per week for this 30-concert tour of Canada. At the performance in Ottawa, Gauthier's hometown, Albani recognized her protégé's obvious talents by stating, "As an artistic legacy to my country, I leave you Éva Gauthier". Albani took a special interest in Gauthier's singing career, giving her advice on care of the voice and similar matters.
Through her connections with the Lauriers and Albani, Éva obtained assistance from many high-placed individuals. Around 1906 Lord Strathcona, Canada's High Commissioner in London, provided her with a scholarship, which enabled her to study and perform in London and Europe. Despite making numerous concert appearances, Gauthier did not make her opera debut until 1909 in Pavia, Italy, when she successfully sang the role of Micaela in Carmen. Afterwards, Gauthier returned to singing in recital with various European orchestras. She did attempt a second grand opera role, but gave up on opera altogether after suffering a significant disappointment.
She had prepared the role of Mallika in Léo Delibes' Lakmé for the London Covent Garden opera company in June 1910. However, she received a shock on opening night when the director informed her that she was being replaced at the demand of the prima donna soprano Luisa Tetrazzini, who feared Gauthier's voice would overpower her own. Rather than give in to such artistic blackmail, Gauthier quit the company altogether.