Career

Giannakopoulos joined the youth team of English club Blackburn Rovers in 2009. He soon however was released and returned to his country joining Panionios. On 27 August 2012, he made his league debut against Aris.

On 29 July 2015, Giannakopoulos signed his four (three years with an option for an additional one) years" contract with Greek giants Panathinaikos for €180,000.