Mirosław Janowski studied at the Fryderyk Chopin Academy of Music in Warsaw. From 1984 to 1995 he was assistant chorus master, then chorus master with the Teatr Wielki in Warsaw. In 1995 he became chorus director with the Roma Music Theatre in Warsaw, yet returned to the Teatr Wielki – Polish National Opera in 1998.
In the course of his career he has prepared choruses for over 100 opening nights and 2000 performances directed by Willy Decker, August Everding, Achim Freyer, Harry Kupfer, Keith Warner, Robert Wilson, Mariusz Treliński, Krzysztof Warlikowski, Mark Weiss, Michał Znaniecki and such conductors in the pit as José Cura, Enrique Diemecke, Placido Domingo, Patrick Fournillier, Valery Gergiev, Marc Minkowski, Alberto Zedda, Łukasz Borowicz, Gabriel Chmura, Jacek Kaspszyk, Kazimierz Kord, Wojciech Michniewski, Krzysztof Penderecki, Andrzej Straszyński, or Antoni Wit.
He himself conducted choruses in Aida, Boris Godunov, Carmen, The Queen of Spades, The Devils of Loudun, Don Carlos, Halka, King Roger, The Flying Dutchman, Madama Butterfly, Manon Lescaut, Maria Stuarda, Onegin, Paradise Lost, Turandot, Guillaume Tell, and more.
He was involved in the preparation of many operettas and musicals, e.g. West Side Story and Wonderful Town. He also worked for the Walt Disney and Warner Bros film studios. He was the artistic director of the Warsaw-based Harfa Singing Society, conducted the Polish Radio Orchestra and Sinfonia Varsovia, and now records collections of patriotic songs with the Media Choir for the Romuald Traugutt Philharmonics, Warsaw.
In September 2017 he took over as the chorus master for the Polish National Opera.