In May 2017, it was reported that a verbal arrangement had been reached for Lacazette to join Atlético Madrid in the summer of 2017, but that fell through on 1 June 2017, after the Court of Arbitration for Sport upheld Atlético's ban on registering players for two transfer windows (1 January – 2 February 2017 and 1 June – 31 August 2017) that was imposed in July 2016 by FIFA on the club for breaching FIFA rules over the signing of minors. Lacazette was given the number 9 jersey.
On 5 July 2017, Lacazette signed a reported five-year deal for Premier League club Arsenal for a club record fee; Lyon disclosed that the fee was an initial €53 million (£46.5 million) plus up to €7 million (£6.1 million) in potential bonuses. The fee was the largest ever received by Lyon from the sale of a player, beating the €41.5 million (£37.7 million) record set by Corentin Tolisso's transfer to Bayern Munich three weeks earlier. The transfer fee also surpassed the previous Arsenal record €50 million (£42.5 million) that Arsenal paid Real Madrid for Mesut Özil in 2013.
On 6 August 2017, Lacazette made his first appearance for Arsenal in the 2017 FA Community Shield against Chelsea. Despite hitting the post midway through the first half, Arsenal eventually won 4–1 on penalties after the game ended 1–1 at full time. This win constituted his first trophy win at Arsenal. On 11 August, Lacazette made his Premier League debut against Leicester City and scored after 94 seconds to give Arsenal a 1–0 lead in an eventual 4–3 win. Lacazette also managed to score in both of Arsenal's next home games, scoring Arsenal's second in a 3–0 win over Bournemouth, before grabbing a brace for the club in a 2–0 win over West Bromwich Albion. With his goals against West Brom, Lacazette became the first Arsenal player to score in his first three home league appearances for the club since Brian Marwood in September 1988.
Lacazette previously played as a winger for Lyon, before becoming a striker. As well as goalscoring and finishing ability, characteristics of his game are pace, strength, balance, technique, dribbling, link-up play, and ability with either foot. He is also a hard-working player, who presses the opposition and wins the ball back using his defensive skills and tackling ability. Fellow Frenchman Gérard Houllier said in July 2017 that Lacazette "is a bit like" former Arsenal striker Ian Wright.