She studied vocal music with Lokyung Pak at Seoul National University in South Korea and with Roland Hermann at the Hochschule für Musik Karlsruhe in Germany.

[8] She made her European debut with the conductor Philippe Herreweghe in Antwerp, Belgium in December 1999, by singing Mozart's "Et Incarnatus Est" from Great Mass in C Minor as well as his solo motet Exsultate Jubilate.

[10] She was a member of Staatsoper Hannover and performed as Zerlina (in Don Giovanni), Papagena (The Magic Flute), Blonde (The Abduction from the Seraglio), Adele (Die Fledermaus), and Yniold (Pelleas et Mélisande) between 2001 and 2004, before freelancing.

4, Poulenc's Dialogues of the Carmelites (as Sister Constance), Bach's St John Passion, Mozart's The Marriage of Figaro (as Susanna), Idomeneo (as Illia), and Requiem (at Carnegie Hall, Musikverein, and Berliner Philharmonie).

[18][19][20] She has worked with conductors including René Jacobs, Manfred Honeck, Fabio Biondi, William Christie, Philippe Herreweghe, Sigiswald Kuijken, Andreas Spering, Iván Fischer, Zubin Mehta, Myung-whun Chung, Ton Koopman, Giovanni Antonini, Herbert Blomstedt, Kent Nagano, and Riccardo Chailly.

In 2009, Sunhae Im was the soprano soloist for the Pentecost solemn mass celebrated by Pope Benedict XVI at St. Peter's Basilica in Vatican City, where she performed Haydn's Harmoniemesse with Helmut Müller-Brühl.