Tachtsidis is a Greek powerhouse: 6'3 and 86 kg. A defensive midfielder with great technical ability, Panagiotis Tachtsidis came through the ranks at AEK Athens, where he broke into the first team in 2007, signing his first professional contract the same year. He made his debut in a Greek cup tie against Fostiras. His league debut came against Thrasyvoulos Fylis and in doing so he became the youngest player in AEK Athens history, having only celebrated his 16th birthday a few days before. In 2010 he signed a 5-year contract with Genoa. Just a few days into his stay on the Italian Riviera, he was sent on loan to Cesena with the option to buy.

In January 2011 he moved on loan to Grosseto in Serie B. His first appearance for the Tuscan side came on 12 March in a 3-2 win over Pescara, with Tachtsidis laying on two of the goals. A third loan spell followed in summer 2011, this time to Verona where he became a starter in Mandorlini's side. He scored his first goal in Italian football on 11 February 2012 during Hellas Verona v Ascoli. It was here that Zdenek Zeman - then coach of Pescara - first noticed him and, once the Czech returned to Rome he asked director of football Walter Sabatini to sign him. He becomes the fourth Greek to turn out for A.S. Roma after Choutos, Dellas and Eleftheropoulos.

AEK
Tachtsidis was promoted from AEK's youth ranks and signed his first professional contract with AEK on 1 November 2007. Shortly after signing his first professional contract, Tachtsidis made his debut for AEK in the Greek Cup against Fostiras. On 27 January 2009, he became the youngest player to have ever played for AEK Athens in the Greek league when he played against Thrasyvoulos being 16 years and 348 days old. That record has since been surpasses by Taxiarchis Fountas. Tachtsidis scored the winning goal in the 92nd minute to give his team the three points.

Genoa
On 21 April 2010 he completed a move to Genoa C.F.C., that had already been agreed upon in January 2010.

Cesena
On 7 August 2010 it was announced that he will spend one year on loan at A.C. Cesena.

Grosseto
On 2 February 2011, Tachtsidis went to U.S. Grosseto F.C. on loan until the end of the season.

Hellas Verona
Tachtsidis went on a third loan spell to Hellas Verona F.C. for the 2011-12 season. His stay at the club turned out very successful, playing in most of the Hellas Verona's games and helping the club to reach the play-offs for promotion to the Serie A.

Roma
On 19 July 2012, Tachtsidis signed a five-year contract with A.S. Roma, for a fee of €2.5 million. He now plays as number 77 as a Roma midfielder