He started playing the piano at the age of six, later studying under Ludmila Kasyanenko. He graduated from the class of Solomon Mikowsky at the Manhattan School of Music (2011), where he was awarded the Harold and Helene Schonberg Fellowship in 2007-11. He is currently completing doctoral studies in piano under Jerzy Sulikowski and Katarzyna Popowa-Zydroń at the Music Academy of Bydgoszcz, where he also lectures.
His repertoire spans from classical music to avant-garde and multimedia. He has appeared in concert through Europe, North America, and Asia, including at Carnegie Hall's Weill Recital Hall, Yamaha Concert Artist's Hall, Los Angeles, San Diego, and Chicago. In Poland, he has worked with all the leading national orchestras under conductors such as Jacek Kaspszyk, Alexander Liebreich, Wojciech Michniewski, José Maria Florêncio, Szymon Bywalec, and Jerzy Swoboda.
He has participated in leading international music festivals such as Warsaw Autumn, Beijing Modern Music Festival, "Belt & Road" Shenzhen International Music Festival, China-ASEAN Music Week in Nanning, Electroacoustic Music Symposium in Toronto, Craiova Muzicală Festival in Romania, Polish Piano Music Festival in Słupsk, and Brain Festival in Bydgoszcz.
He focuses on the latest contemporary music. With jazz pianist Christian Sands (member of the Christian McBride Trio), he founded the 3xPiano project (2009-11), combining elements of jazz, classical, and electronic music. He has been working with Polish composer Stefan Węgłowski, participating notably in the latter's CD Contemporary Jewish Music (Kairos).
Adam Kośmieja is also a music promoter, acting as artistic director of the International Contemporary Music Seminar in Bydgoszcz, which he founded in cooperation with the Feliks Nowowiejski Music Academy in Bydgoszcz in 2014. He has been awarded scholarships from the Polish Minister of Culture, Mayor of the City of Bydgoszcz, and Marshall of the Kuyavian-Pomeranian Voivodeship.