She was a student of Oszkár Maleczky and Jenő Sípos at the Academy of Music in Budapest between 1961 and 1966; she won first prize at the Erkel International Voice Competition while still being a student at the Academy.
After finishing her studies in Budapest she earned a scholarship at the Opera in Stuttgart in 1966; in the 1970s she was a member of the Deutsche Oper am Rhein in Düsseldorf. Her international career began in 1966 already, when she sang the alto solo of the Johannes Passion at the Viennese Festival Weeks by the invitation of Karl Richter. In 1971 she sang the same oratorio also at the Academy of Music - under the baton of Wolfgang Gönnenwein considered being a young talent at that time – ‘representing worthily the craftsmanship and professional standards.' She convinced her audience about her musicality and knowledge of style with intimate, personal and emotional performances of several Bach Cantatas at her guest appearances in Budapest later.
She sang Mercedes in the Carmen in Salzburg in 1967 already with Karajan conducting, and since then she is one of the most sought after oratorio-soloist and Lied singer of Europe as well as being guest artist of several opera houses. She is characterized by a beautiful voice material, great knowledge of singing, brilliant virtuosity, excellent acting and a grand ability for characterization with first-class skills for style, above all.
Her international career evolved in a fast tempo: she sang Dorabella at the Flandria Festival, and then the great Rossini-roles in a sequence (L'italiana in Algeri, La Cenerentola, Le Comte Ory, The Barber of Seville) directed by Jean-Pierre Ponelle. She sang the role of Sextus in the famous Titus -performance of the Cologne Opera also with Ponelle and István Kertész conducting, which was one of her greatest successes. The Titus were performed in Budapest, as well by the Cologne Opera in a guest appearance with superb powers and Júlia Hamari in the place of honor among them, but we could hear excerpts also from Händel's Giulio Cesare in a concert performance with her amazing virtuosity and impressive technical security.
She performed with the greatest conductors of the world regularly (Giulini, Abbado, Muti, Jochum, Kubelik, Solti, Doráti, Rilling and others) and at the most significant festivals (Salzburg, Edinburgh, Vienna, Munich). Her performance in the Orfeo-production of the Maggio Musicale Firenze was such a great success that it had to be repeated the following year, as well.
She sang the breeches part of the I Capuleti e i Montecchi an opera of Bellini so matching for her, in two concert performances on the occasion of her artistic career's thirty-fifth anniversary (and her fiftieth birthday).
A special place in her career was taken by Lieder that she sang with a full transubstantiation at her recitals meaning the great hours of performing art. She explored the realm of that genre comparably to her greatest colleagues and her knowledge of style is crystal clear. She felt and made the audience felt the primary meanings of the keywords of Romanticism (night, death, moonlight, wandering) in their deepness. ‘Not the genre, not the situation neither the humor is the main area of Júlia Hamari, but that kind of song poetry which can be approached only spiritually, that makes the almost reverential expression of emotions possible.'– said György Kroó following the artist's song recital in 1979 in Budapest. Her interpretation of the Bluebard's Castle - at an opening performance of the Budapesti Művészeti Hetek (Budapest Weeks of Art) under the baton of Ferencsik and with the young László Polgár singing the title role – was memorable.
She has been engaged by the great recording companies (DG, EMI, Decca, Phillips and CBS) since the beginning of her career. She sang title roles of entire operas and oratorios on the recordings and made several solo recordings, as well.