Gjersvik was born in Bergen, Norway, where he studied at the Grieg Academy and Bergen Conservatory of Music, where he has also taught. As a performing musician, he has led his own trios, quartets and quintets as well as tango orchestra Combo Tango. Gjersvik is very versatile and has played with musicians like Kaizers Orchestra, Ketil Bjørnstad, Ole Thomsen, Kåre Thomsen, Ole Paus, Jan Eggum, Herborg Kråkevik and Sissel Kyrkjebø.He has also been widely used in theater and television connection, and has participated on many albums. Under his own name, he has published A Voice from the Past (1990) and Milonga Triste (1998) among others, and Combo Tango Plays Music by Ole Amund Gjersvik (2002). He has received numerous awards and honors, including Rolf Gammleng Award in 2000. In 1990 he founded his own label, Acoustic Records.