He made his debut in Europe's continent-wide second-tier level competition, the EuroCup, with Panellinios, during the 2007–08 season.

[8] On 16 May 2015, Pappas suffered a torn ACL injury, and a tear of his meniscus, in a Greek League game against Kolossos Rodou, after falling awkwardly, after being fouled on a play by Vassilis Toliopoulos.

[10] During a press conference on July 3, 2020, it was confirmed by the team's new head coach Georgios Vovoras that Pappas was parting ways with the Athenian club after seven seasons.

On September 23, 2020, Pappas signed with Hapoel Jerusalem for the duration of the Basketball Champions League Final-8.

[13] He was constantly plagued by injuries and he also spent the final stretch of the season under suspension, after falling out with new coach Curro Segura, who took over the team after Stefanos Dedas signed with CSKA Moscow.

In 12 league games, he averaged 12.4 points, 2.5 rebounds, 2.8 assists and 1.4 steals, playing around 27 minutes per contest.

After assisting the team in the pre-season, on December 3, 2022, Pappas was signed on for the rest of the 2022–2023 campaign in order to close out his playing career with his beloved Panathinaikos.

Reportedly, Pappas pledged to donate the entirety of his contract pay to the sanitation workers at the Athens Olympic Stadium complex.

As a member of the junior national basketball teams of Greece, Pappas won the silver medal at the 2007 FIBA Europe Under-18 Championship.

On 19 August 2017, he scored 22 points (career high with the senior Greek NT) in a friendly game against Great Britain, in London.