First learned to play the guitar when he was eight and later enrolled in the National Conservatory of Greece, studying with Dimitri Fampas.
He studied at the Royal Northern College of Music under Gordon Crosskey and John Williams (classical guitar), as well as with pianist and conductor George Hadjinikos (advanced theory and music analysis), obtaining a Postgraduate diploma from the University of Manchester.
As a classical guitar soloist, he has appeared in concerts (onstage or via electronic media) in Greece, in most European countries, in America, and the Far East.
[1] He has been a long-time collaborator of such Greek composers and songwriters as Manos Hadjidakis,[2] Mikis Theodorakis, Nikos Mamangakis and Kyriakos Tzortzinakis, singers such as Savina Yannatou, Aliki Kayaloglou, Maria Dimitriadi and Nena Venetsanou, as well as significant Greek and foreign performing musicians.
Kostas Grigoreas' compositional oeuvre lays emphasis on the classical guitar as a solo instrument or as part of an ensemble.