He made his senior debut in 2019, at the Cup semi-final against PAOK in which he played the whole game but he conceded 3 goals as Olympiacos lost 3–2.

Tzolakis made his league debut in a game against Aris getting subbed on in the place of Bobby Allain in the 78th minute.

On 21 July 2021, Tzolakis made a crucial save and kept a clean sheet in his European debut against Neftchi Baku in a 1–0 home win on the 2nd qualification round of UEFA Champions League.

[3] On 18 April 2024, Tzolakis was the undisputed hero in the qualification of Olympiacos for the semi-final of the 2024 UEFA Europa Conference league, saving three penalties in a 3–2 winning shootout away at Fenerbahçe, following a 3–3 aggregate draw.

[4] He was also a key figure in helping his team lift the Conference League, as his saves played a large part in the Reds' 1–0 victory over Fiorentina after extra time, in the final held at OPAP Arena, Athens.