Early career Athanasiadis returned to the junior squad in
PAOK in August 1998 and worked his way through the ranks of the academy, showing his scoring abilities and talent with the ball, with the help of junior coach Kostas Malioufas, who established him as a striker. He moved to the Reserve Team in 2004. His hard work under coach
Kyriakos Alexandridis was praised in the 2006–2007 season when he became top scorer with 24 goals, with PAOK dominating the Reserve League. His performances earned him a professional contract for three years. He debuted with the first team on 24 February 2007 in a home match against Larissa, coming in as a substitute, with PAOK losing the match 1–3. Coincidentally, his first game as a starter for PAOK was again against Larissa at the last game of the 2007–2008 season where he scored 2 magnificent goals in the first half, with Larissa defeating PAOK again by 4–3. He also renewed his contract in 2008 for a further 5 years. He was working hard to find a place in the starting eleven, yet was overshadowed by more experienced players like
Zlatan Muslimović and
Lambros Choutos and was mostly used as a late substitute by
Fernando Santos. On 29 November 2008 against
Thrasyvoulos, Athanasiadis came off the bench in the 89th minute and went on to score the winning goal four minutes later, to win the match 1–2. In 2009, he was loaned at
Panserraikos as new strikers arrived at PAOK and he was not a part of Santos' plans. He needed to gain experience as a hot prospect for the future. He got 22 caps in the
Football League scoring 5 goals. He scored a goal in the
Greek Cup victory 3–1 over
Olympiacos.
PAOK In
2010–11 season he returned to
PAOK. He got 4 European caps mainly as a substitute. He scored his first goal of the season at the first game played in the newly built
AEL FC Arena as a substitute, giving PAOK a 1–2 victory over
AEL. On 4 August 2011 he scored his first European goal with PAOK in the game with
Vålerenga in a 3–0
Europa League victory. On 18 August he scored again, this time against
Karpaty Lviv. On 30 November he scored against
Tottenham Hotspur, with the second goal for PAOK in a surprise 2–1 victory at
White Hart Lane in the Europa League, when he met a low cross from
Giorgios Georgiadis. In
2012–13 season he scored goals in matches against fierce rivals
Aris and
AEK Athens while also scoring the equalizer in a 1–1 home draw against
Olympiacos. Athanasiadis scored his first hat-trick against
Kallithea on 24 January 2013 in a 6–0 win. After the departure of
Pablo Garcia he was named vice-captain of the club behind
Dimitris Salpingidis, wearing the captain's armbrand on many occasions. On 17 April 2013 he went on to give an assist and score a goal against
Asteras Tripolis in the first leg of the
Greek Cup semi-finals. He entered the
2013–14 season by scoring in a 3–0 home win against
Skoda Xanthi. On 12 September 2014, Athanasiadis renew his contract with PAOK till the summer of 2018. He now had a huge contract, one of the two largest in the roster, his annual salary more than tripled (from €180,000 to more than €700,000 per year!). Athanasiadis stated: "I'm happy because I closed an issue that had taken time to resolve. With my signature I think not only me but the entire family of PAOK are happy", and continued: "I want to thank some people who helped make this happened. The major shareholder Mr. Savvidis, the technical director
Zisis Vryzas and the president of the club." On 18 September 2014, he scored an 18-minute hat-trick in a 6-1 home win against
Dinamo Minsk in the Europa League group stage. This made him the first ever player to score a hat-trick for PAOK in a European match. He added another two against the same opposition away on 27 November, scoring late goals in the 82nd and 88th minutes to win the game for PAOK. On 11 December he scored a penalty to equalise in a home group game against
Guingamp for his sixth of the tournament, but the French team won 2-1 and advanced at PAOK's expense. On 4 July 2015, during a friendly game in the training period, he suffered an overwhelming intra-articular fracture of the first toe of the right foot, that caused him (according to the officials' reports) an absence of approximately 4 to 6 weeks. On 12 September 2015, he returned to the starting XI in the third day of the
Super League Greece in an away 3-0 win against
Veria, by scoring the first goal. Athanassiadis, with this goal against Veria, made it four consecutive seasons he had scored in his first game of the Super League. On 23 September 2015, he scored the winning goal with a penalty kick in a home derby against rivals AEK Athens. On 30 November 2015, a brace from Athanasiadis helped PAOK win 3-1
AEL Kalloni at Mytilini, with
Giannis Mystakidis also scoring in the last minute of the game. The home team had temporarily equalized with a penalty kick by captain
Yiorghos Manousos. On 20 December 2015, with a penalty kick he scored the goal to give PAOK a hard-fought 1-0 home win against brave
Platanias, who had created many chances to equalize. On 17 January 2015, Athanasiadis' goal against Veria in the 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
Super League Greece statistics, Athanasiadis was shown 49 yellow cards between 2012 and 2016, an incredible number considering that he played mainly as striker. On 26 May 2016 he scored a brace in a 2-0 home win against Panionios in the
play-offs exceeding 100 goals in PAOK colours in all competitions. On 3 August 2016 he scored against
Ajax in the
Uefa Champions League 3rd qualifying round. However, his team lost 2-1 and got knocked out of the competition. On 29 September 2016, Athanasiadis netted both goals as PAOK recovered from a nightmare start in the Europa League group stage against
FC Slovan Liberec when Russian
Nikolay Komlichenko scored the opening goal for Slovan in 41 seconds. He finished the
2016-17 season without being able to score for the club in the Super league. The last time a first-choice striker went a full season for the club without scoring was 1978 with
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.
Maccabi Haifa On 22 August 2017, Athanasiadis completed his move to
Maccabi Haifa. The 28-year-old Greek International was released from
PAOK and signed a 2-year deal with the Israeli club. He was reportedly set to earn €550,000 per year, plus bonuses. On 21 October 2017, he scored his first goal with the club in the last minute of the game, coming as a substitute in a 2-1 home loss against
Beitar Jerusalem. On 8 January 2018, Athanasiadis netted home the winning penalty to send Maccabi Haifa to the Last 16 of the
Israeli State Cup. He had had a disappointing spell in Israel since joining the club over the summer, but was the hero on this game for the Haifa side. On 23 August 2018, after a rather mediocre season, he mutual solved his contract with the club.
PAS Giannina On 7 September 2018, after his departure from Maccabi Haifa, Athanasiadis eventually found himself a new club, penning a two-year deal with
PAS Giannina. On 1 December 2018, after a cross to the left from
Giorgos Pamlidis, Athanasiadis scored, sealing a 1-1 home draw against
OFI Crete F.C., his first goals in the Greek top flight since May 2016 (two goals against Panionios with PAOK) and after a 32 game goal drought in the Super League. On 9 February 2019, he scored after
Alexandros Nikolias’ cross left Pananthinaikos goalie
Sokratis Dioudis with no chance to react to a clinical header, sealing a vital 1-0 home win game in his club's effort to avoid relegation. On 26 June 2019, he mutually dissolved his contract with the club.
Later years On 22 October 2020, Athanasiadis who had last played in the Greek second division for
Panserraikos F.C. in the 2009-10 season, joined
Apollon Larissa. The 32-year-old striker was without a team for over a year. On 18 August 2021 he signed a contract with
Super League Greece 2 club
Anagennisi Karditsa ==International career==