The imposing form of first-choice keeper Antonios Nikopolidis and the presence of Józef Wandzik, Kostas Chalkias and Mario Galinović kept Kotsolis most of that time at the bench.

He made his professional debut for Panathinaikos on 13 April 1999, in a Greek Cup game against Athinaikos.

[2] During season 2006/2007, he won the Greek Cup after beating his former club Panathinaikos at the final.

On 26 April 2014, Kotsolis won his third Greek Cup playing at the final against PAOK.

[3] He is a former Greece under-21 international and team captain at the 2002 UEFA European Under-21 Football Championship.