[1] Shortly after signing his first professional contract, Tachtsidis made his debut for AEK in the Greek Cup against Fostiras.

Against Thrasyvoulos, Tachtsidis scored the winning goal in the 92nd minute to give his team the three points.

[2] On 21 April 2010, Tachtsidis completed a move to Italian club Genoa that had already been previously agreed upon in January 2010.

[32][33] On 19 September 2017, he made his debut with the club in a Greek Cup 2–1 home win game against Asteras Tripolis.

On 7 February 2018, Tachtsidis grabbed a goal back from a set-piece for Oscar Garcia's Olympiacos, but the reds could not find a way back and waved goodbye to a chance of silverware with AEK progressing to the Greek Cup semifinals 2–1 on aggregate after the first leg ended 0–0.

[34] On 5 September 2018, Tachtsidis signed for EFL Championship side Nottingham Forest on a two-year deal.

The Greek midfielder had found his opportunities hugely limited at the City Ground, following his arrival from Olympiacos.

The 27-year-old has featured on the bench – but has not had any minutes on the pitch, amid fierce competition for places in Aitor Karanka's squad.

[43] On 30 September 2022, Tachtsidis joined UAE Pro League side Khor Fakkan.

One person was killed in the collision, but the Greek Federation released a statement confirming that the three players were not seriously injured.

[47] On 11 October 2015, he scored his first goal with Greece in a 4–3 home win against Hungary when he lashed in a powerful shot.