While still a student of Josip Novosel in 1974, Mario Ivelja started his professional career in Zagreb Philharmonic, where he became leader of bass division in 1978. In january of 1979, he was invited to become full-time member in Zagreb soloists. As a both chamber musician and soloist in Zagreb Soloists, he toured the whole world and performed in most renowned concert halls. He collaborated with famous musicians, such as Henryk Szeryng, James Galway, Ugo Ughi, Leo Nucci, Isabelle Moretti, Radovan Vlatković and so on.
As a soloist he performed with many croatian ensembles and orchestras (Zagreb Philharmonic, Dubrovnik Symphony Orchestra, Croatian Chamber Orchestra, Split Chamber Orchestra etc). He presented to Europe and USA works for double bass by Papandopulo, and first performed his Concert for double bass and strings (integral version), and also works by Klobučar and Palanović. He also recorded music for Croatian National Television, works by Kelemen, Uhlik, Matz, Piazzolla etc. He’s a professor at Music Academy in Zagreb, and also founding member and artistic director of Croatia’s first double bass ensemble called L’Éléphant Quartet.