Arsenal were beaten 4-2 today by Watford in a behind-closed-doors friendly. Goals from Marquinhos and Eddie Nketiah gave the Gunners a 2-1 at the break.
However, the Championship side returned and snatched victory. Keinan Davis, Yaser Asprilla and Joao Pedro were on target.
The game at London Colney was the team's first since beating Wolves three weeks ago in the Premier League.
Arsenal will travel to Dubai for a mid-season tournament.They return to domestic action on Boxing Day against West Ham.
Arsenal: Hein (Graczyk 58), Cedric (Walters 46), Holding (Foran 46), Gabriel (Monlouis 46), Tierney (Sousa 46), Elneny (Lewis-Skelly 46), Lokonga (Nwaneri 46), Odegaard (Smith 46), Nelson (Butler-Oyedeji 46), Marquinhos (Sagoe Jr) 46), Nketiah (Cozier-Duberry 46). Subs not used: Awe, Cirjan, Ideho.