Pappas studied at the University of Strathclyde and completed his PhD there in 2013, having written his thesis on the topic of the macroeconomic impact of projected population changes in Greece. In 2015, the University of Strathclyde Students' Association awarded Pappas lifetime membership for doing "inspiring work" to "rebalance the economic injustices facing working people".[3]
Pappas was a minister of the government of Alexis Tsipras.[5] They first met at a meeting of Synaspismos Youth when they were 19.[4] He later became Tsipras' chief of staff.[6] He was appointed as a Minister of State in the First Cabinet of Alexis Tsipras.[5] On 24 February 2023, Pappas was convicted by a Special Tribunal to two years in prison for the crime of breach of duty relating to his handling of television broadcast licenses during his tenure as Minister of Communications in the government of Alexis Tsipras from 2015 to 2019.
In 2023 he participated in the 2023 Syriza leadership election being eliminated in the first round coming second to last with 12,787 (8.7%) later endorsing Stefanos Kasselakis who ended up winning the election and becoming leader of the party.[7]