He was born as the son of a danish mother and a greek father in Hermoupolis (Greece) in 1964. After studying piano at Thessalonica New Conservatory and musicology at Copenhagen University, he went on to graduate with distinction from Vienna Academy of Music as a conductor and répétiteur, and attended masterclasses with, amongst others, Leonard Bernstein, Vaclav Neumann and Rolf Reuter. He speaks eight languages.

After his first engagement as assistant conductor and director of studies at Meiningen State Theatre, in 1996 Stefanos Tsialis received a scholarship from the Richard Wagner Foundation. From 1997 to 2004, he was chief conductor of the Central German Chamber Philharmonic, while from 2001 to 2004 he was also permanent guest conductor of the Berlin Symphony Orchestra. He subsequently returned to Meiningen State Theatre as First Kapellmeister and Deputy General Music Director from 2005 until 2009. From 2009 to 2013, he was Chief Conductor and Artistic Director of the Thuringia Philharmonic in Gotha whereas from 2015 till 2019 he was its permanent guest conductor. He also served as the Chief Conductor and Artistic Director of the Athens State Orchestra from 2014 to 2020.