On 12 April 2019, Papastathopoulos was named to the UEFA Europa League's 'Team of the week' after playing a vital role in Arsenal's 2–0 win over Napoli in the first leg of the quarter-finals. He was one of four Arsenal players selected along with Petr Čech, Ainsley Maitland-Niles, and Aaron Ramsey. On 24 April 2019, Papastathopoulos scored his maiden goal in the English Premier League via a close-range header from a corner kick, but Arsenal slipped to a 1–3 defeat against Wolverhampton Wanderers. On 29 May 2019, he started in the 2019 UEFA Europa League Final against Chelsea which Arsenal lost 4–1. This was the first time Arsenal had conceded four goals in a European match since a 5–1 loss to Bayern Munich in March 2017.