Hull City's willingness to break their transfer record twice over — the previous mark was the £13m paid to Tottenham for Ryan Mason back in 2016 — reflects just how far Tzolakis's stock has risen since breaking into Olympiacos's side in 2020.
Although neither side has confirmed the fee, it is thought to be around £20m plus add-ons.
A boyhood arrival at the club's academy from local side Platanias, he grew into the guaranteed number one for a Greek giant that had never lifted a European trophy, and it was Tzolakis's penalty-shootout heroics against Fenerbahce, followed by a clean sheet in the final win over Fiorentina, that finally delivered the 2023-24 Conference League and turned him into a national hero.
Individual recognition followed the next season, when he swept the Greek Super League's Player and Goalkeeper of the Year awards on the back of a campaign in which he barely missed a minute of league football, added nine Champions League outings, and finished with 23 clean sheets from 43 games in all competitions.
Add four league titles, a domestic cup and a Super Cup to that Conference League triumph, and a total haul of eight trophies in five and a half seasons, and it becomes clear why a fee in the region of £20m plus add-ons was needed to prise him away — figures neither club has confirmed. His rise has been mirrored at international level too: nine caps since a June 2024 debut against Malta, most recently featuring against Sweden this summer.
"I am very happy to be here. It's a big honour to join Hull City. I am ready for a new chapter in my career," Tzolakis said. "I met all the players and staff in Turkiye, and I thank them for the warm welcome. With Olympiacos, I had a successful career with a Conference League title, championship and a cup, also European games and Champions League.
"Hull City is something different because we are playing in the Premier League. We have to fight against top players, so it's a challenge for me. I feel ready. I will give everything I have every single day in training to help our team achieve its goals. I'm excited to be in England.
"I wanted to come to Hull City because the Premier League is the top stage. I know Hull have passionate supporters, so I can't wait to play for them."
Elsewhere at the club, double promotion-winning academy favourite David Meyler has returned to Hull as a Professional Development Phase coach, partnering lead PDP coach Conor Sellars with the Under-21s for the coming season.
Meyler, who scored 19 goals in 191 appearances for the Tigers as a player, previously worked in the academy from March 2023 before leaving in May 2025 to become first-team assistant manager at Cork City, where he helped guide the club to the 2025 FAI Cup final and had them sitting top of the Irish First Division, 15 points clear of second place, at the time of his departure.
"It has been a bit of a whirlwind 12 months," Meyler said. "I had an incredible experience in Ireland, with ups and downs, a relegation and a cup final, and when I recently left we were clear at the top of the table, which is really positive, but to come back and keep going round in this circle - I am excited and looking forward to it, as there is a really good group of players in the Under-21s.
"Hull is home. I have been based here since 2012, so 14 years is a long time. I got married here, my kids were born here and I am extremely settled. This football club means so much to me, and I'd like to think I am giving something back to it."