After a summer of speculation, Torreira joined English club Arsenal on 10 July 2018 for an undisclosed fee, believed to be around £26. 4m. Upon the completion of the signing, head coach Unai Emery said "A midfielder with great quality, I have enjoyed watching his performances for Sampdoria in the past two seasons, and we all saw him do very well for Uruguay in the World Cup. He is a young player already with good experience, but who wants to keep on growing. " Torreira was given the number 11 shirt, previously worn by Mesut Özil, who took the vacant number 10, following the departure of Jack Wilshere. Torreira made his Premier League debut on 12 August, coming on as a substitute on the 70th minute in a 2–0 defeat to Manchester City. Torreira registered his first assist of the season, by setting up Alexandre Lacazette's winning goal in a 3-2 win over Cardiff City. Torreira made his full-debut and his Europa League debut for Arsenal in the 4-2 win over FC Vorskla Poltava, before being replaced in the 57th minute by Mattéo Guendouzi.