Inez Hafkamp studied at the Royal Conservatory in The Hague with Marianne Dieleman and Herman Woltman. After her studies she was accepted to the Chorus of Dutch National Opera in 1990. Since then she has performed as a soloist with DNO in Die Frau ohne Schatten (1996, 2008), Life with an Idiot, Rosa, a Horse drama, Die Meistersinger von Nürnberg, Alice in Wonderland, Kát'a Kabanová, Lohengrin, Der Rosenkavalier, Idomeneo, Parsifal and Der Schatzgräber.
Inez also contributed to a large number of oratorio works, such as Bach's Passions, Saint-Saëns' Oratorio de Noël and Rossini's Petite Messe Solennelle. She also performed in Orfeo ed Euridice (Switzerland, the Netherlands), Parsifal (Belgium) and in De Stijl by Louis Andriessen with the Nederlands Blazersensemble.