On 15 July 2010, in Tirana, Albania, he made his first appearance in the Europa League against Besa Kavajë, replacing Jaouad Zairi in the 75th minute.

Fetfatzidis scored his first European goal in the home match against Besa Kavajë in G. Karaiskakis Stadium in a high-scoring victory for Olympiacos.

Fetfatzidis scored his first goal in the Greek Super League against Skoda Xanthi on 16 October 2010, replacing Dennis Rommedahl in the match.

In September 2013, Fetfatzidis joined Serie A club Genoa for a reported €4 million transfer fee which made him the most expensive Greek player to move out of the Super League.

The Giallorossi got a number of chances to open the scoring, but were made to pay for their profligacy in front of goal by Giannis Fetfatzidis' winner.

On 8 August was a starter in a 5–3 on penalties after a 1–1 draw in London Fulham's stadium Craven Cottage against Al-Hilal winning the Saudi Super Cup.

[16] On 13 March 2017, he scored the second goal of his club giving a lead for a final 2–2 home draw against Al Ain in the AFC Champions League.

On 12 May 2017, one month after the renewal of the contract with Al-Ahli, Fetfatzidis scored a goal which paved the way to qualifying for the final of the King Cup in a glorious 3–0 win against Al-Faisaly.

[23] On 15 September 2019, in a home match against Panathinaikos, Fetfatzidis made his best performance as an Aris player, scoring one goal and giving 2 assists, helping to a stunning 4–0 win.

[24] On 8 December 2019, Fetfatzidis, who was arguably the game's best player, scored an added time equaliser to cap a fine individual performance and secure a valuable 2–2 away draw for Aris against Atromitos.

[29] However, due to the terms alteration by Al Ain, concerning the transfer fee and Fetfatzidis' wage, the deal fell off and the Greek winger will remain in Thessaloniki.

[38] Fetfatzidis made his debut with Greece in UEFA Euro 2012 qualifying, participating in the 1–0 win over Latvia on 8 October 2010 at the G. Karaiskakis Stadium as an 82nd minute substitution for Sotiris Ninis.

On 9 February 2011, he scored his first goal for the national team at the AEL FC Arena in Larissa in a friendly match against Canada that Greece won 1–0.

[39] On 31 March 2015 three Greece players (Fetfatzidis, Moras, Tachtsidis) suffer minor injuries after being involved in fatal car crash following Euro 2016 qualifier 0–0 with Hungary.

At 5'5" he has a medium build that further facilitates agile mobility, Fetfatzidis possesses great vision that allows him to provide assists to accompanying forwards.