On 6 June 2017, Premier League club Arsenal confirmed the signing of Kolašinac on a free transfer, pending the "completion of all regulatory processes." Kolašinac scored on his debut against Chelsea in the 2017 FA Community Shield, which Arsenal won on penalties. He made his Premier League debut on the opening day, providing an assist in a 4–3 win over Leicester City. For his performances in August, he was voted as Arsenal's Player of the Month, earning more than half of the votes. On 14 September, Kolašinac scored on his UEFA Europa League debut against 1. FC Köln, which Arsenal won 3–1. He scored his first goal in the Premier League on 28 October against Swansea City, and also provided an assist for his team's other goal in a 2–1 victory. Kolašinac was once again voted as Arsenal's Player of the Month, in October, earning half of the votes.