The daughter of a conductor father and a musical singer mother, she was born into and grew up in a musical family.She made her musical debut at twenty three with a joint concert with the Korean Symphony Orchestra. She then performed in numerous Korean musicals on national stage, for which she has recieved numerous awards.However, because of all its constraints she did not find that musical environment fulfilling.
She decided to go to Paris in 1995 to study jazz and French chanson at the CIM school - one of the oldest jazz schools in Europe - and at the National Music Institute of Beauvais, and at the Nadia and Lili Boulanger Conservatory. Her innate talent for jazz revealed itself when she started playing in Parisian jazz clubs with her group YSN 5Tet(which was formed in 1996).
She made her rounds around the Paris club scene. performances that would earn her invitations to work together with many famous musicians. Youn Sun Nah made a strong showing in a number of jazz competitions like La Defense, St. Maur and Montmatre. She became the buzzword in theatres and festivals all over France, while also performing in Korea, essentially managing simultaneous careers in two countries.
Producing five albums in six years, she held numerous performances in France, Europe and in Asia, including Korea. Such vigorous activity would earn her the best artist prize in in crossover music category in Korea in 2003