After a very successful debut as Pamina in Mozart's The Magic Flute (Die Zauberflöte) she joined the Latvian National Opera as a soloist, where she performed parts such as Mimi in Puccini's La Bohème and Gilda in Rigoletto and took on title roles in Lucia di Lammermoor and Handel's Alcina.

In 1999, Inga Kalna became a soloist of the Hamburg State Opera, where audience came to appreciate her convincing performances as Olympia, Antonia and Stella in Offenbach's Les Contes d'Hoffman, Adina in Donizetti's L'Elisir d'amore, as Lucia in Lucia Di Lammermoor, as Gilda in Verdi's Rigoletto as well as a breathtaking Violetta in La Traviata. She enchanted the Hamburg audience in operas such as La Bohème, Boris Godunov, Dialogues des Carmélites, Turco in Italia among many others. In London she made quite an impression as La Contessa in Mozart's Le Nozze di Figaro, with the orchestra conducted by Sir Colin Davis. Other engagements have taken her to the Vienna State Opera, Nederlanse Opera, The Vlaamse Opera, Bavarian Opera, the opera houses in Zurich, Lausanne, Toulouse, Madrid, Barcelona and the Bolshoi Theatre in Moscow. She made her Salzburg Festival debut in 2006 as Die erste Dame in Die Zauberflöte under maestro Riccardo Muti. A year later she was heard as Handel's Alcina at the Opera National de Paris. In 2009, she made her La Scala debut in the same role.

Inga Kalna enjoys particularly close working relationship with two conductors: under Rene Jacobs she appeared at the Dresden Music Festival, the Innsbruck Early Music Festival, the Berlin State Opera and the Festival in Aix-en-Provence; under Marc Minkowski she has been heard as Alcina at Vienna State Opera, as Piacere (Handel's Il trionfo del Tempo) at the Berlin State Opera, Vitellia (Mozart's La clemenza di Tito) at the Theatre du Capitole in Toulouse and as Cinna (Mozart's Lucio Silla) at the Salzburg Festival and La Scala. The artist has worked with conductors such as Sir Colin Davis, Riccardo Muti, Gerd Albrecht, Marc Soustrot, Ivor Bolton, Alfred Eschwe, Ingo Metzmacher, Stefan Soltesz, Harry Bicket, Simone Young, Andrea Marcon, Andris Nelsons, Mikhail Pletnev, Giovanni Antonioni, Ottavio Dantone, Julian Reynolds, Paolo Arrivabeni, Attilio Cremonesi, Maurizio Benini and many others.

Inga Kalna is also much sought after for her masterclasses, which she gives regularly in Riga. On CD Inga Kalna may be heard as Armida (Rinaldo) and Die Erste Dame (Die Zauberflöte) under Rene Jacobs, as Asprano (Motezuma) under late Alan Curtis, Regina (Hindemith's Mathis der Maler) under Simone Young and Romilda (Serse) under Maxim Emelyanichev. In 2021, for the album Das Rosenband, recorded under the label SKANI with pianist Diana Ketler, Inga Kalna received the Opus Klassik nomination in the category Singer of the Year.