[1] Nathanael was born in 1978 in Thessaloniki to Irene and Vasilios Symeonides.
In 2003 he graduated from Hellenic College and became a deacon, and in 2010 he was ordained as a priest.
In 2016 he served as the director of the Office of Inter-Orthodox for the Interfaith Relations at the Greek Orthodox Archdiocese of America in collaboration with the Council on Foreign Relations.
[1] As bishop, Nathanael has called for more active engagement of the church with the youth.
[3][4] On September 7, 2024, two days before the one year anniversary of the opening of Chicago's first casino, Nathanael denounced legalized gambling, stating it "Disrupts our brain, [and] degrades our dignity".