On 17 January 2015, Athanasiadis' goal against Veria in the Greek Super League was the 100th official for the Greek striker in less than eight years after his first in April 2008. On 13 February 2016, according to medical staff Athanasiadis suffered a hamstring strain injury during Greek Cup match against Panionios and will remain out of action for 15–18 days. According to Superleague Greece statistics Stefanos Athanasiadis has been shown 49 yellow cards the last four years, an incredible number if we consider that he is playing mainly as striker.49 yellow cards in four years for Athanasiadis Retrieved 5 April 2016 On 26 May 2016 he scored a brace in a 2-0 home win against Panionios in the play-offs exceeding 100 goals with the jersey of PAOK in all competitions.ΠΑΟΚ- Πανιώνιος 2-0, με πάρτι του Κλάους Retrieved 26 May 2016 On 3 August 2016 he scored against Ajax in the Uefa Champions League 3rd qualifying round. His team lost 1-2 and got knocked out of the competition. On 29 September 2016, Klaus netted both goals as PAOK recover from nightmare start in the Europa League group stage against FC Slovan Liberec when Russian Nikolay Komlichenko scores opening goal in 41 seconds in a 2-1 PAOK away win.Liberec 1-2 PAOK Retrieved 29 September 2016 He finished the 2016-17 season without being able to score with the club in the Superleague, that had to happen since 1978 with the striker Georgios Kostikos. He started the 2017-18 season as a late substitute in a 3-1 home win game against Östersunds FK at Toumba Stadium in the first leg of the Europa League play-offs.
