There was also a debut for new signing Albert Sambi Lokonga, with the Belgium U21 midfielder getting his first taste of action in a Gunners’ shirt.
Chambers put Arsenal in front in the first half by tapping into an open goal after Pierre-Emerick Aubameyang had blasted against the bar with an overhead kick.
Arsenal captain Pierre-Emerick Aubameyang played a big role in the win without scoring
Aubameyang set up Calum Chambers’ opener when he struck the bar with this overhead kick
Albert Sambi Lokonga made his first Arsenal appearance since joining from Anderlecht
Arsenal (4-3-3): Okonkwo (Hein 46); Chambers, Holding, Mari (Cedric 60), Tierney (Tavares 60); Partey (Maitland-Niles 71), Elneny (Lokonga 46), Smith Rowe (Nelson 71); Pepe (Willian 71), Nketiah (Lacazette 46), Aubameyang (Balogun 71)
Millwall (4-4-2): Long; Romeo (McNamara 60), Ballard (Alex Mitchell 78), Cooper, M. Wallace, Malone (Burey 77), Thompson, Mitchell, Evans (Bennett 60), Bradshaw (Bodvarsson 60), Afobe
Boss Mikel Arteta brought on Lokonga, who joined Arsenal from Anderlecht earlier this month for £15million, while also introducing Lacazette, Nuno Tavares and Karl Hein.
Lacazette made a quick impact when he doubled Arsenal’s lead by heading home a Chambers cross.
Arsenal’s front three then combined for a classy third goal as Aubameyang beat a defender down the left wing and crossed towards Lacazette, who dummied and allowed Pepe to score instead.
Emile Smith Rowe started days after signing a long-term deal with the club and narrowly failed to find the net in the second half.
Alexandre Lacazette made a quick impact when he doubled Arsenal’s lead at London Colney
Nicolas Pepe scored Arsenal’s third goal in the behind-closed-doors game at London Colney
Twenty-year-old striker Balogun got the fourth goal late on after coming off the bench, darting on to a pass from Willian to round the keeper and score.
Millwall got a consolation goal when Alex Mitchell struck in the final few minutes following a corner.
Arsenal’s next friendly is against Chelsea in the Mind Series on 1 August, when the Gunners will be able to welcome an almost capacity crowd at the Emirates Stadium for the first time since the coronavirus pandemic struck.
Twenty-year-old striker Balogun got the fourth goal late on after coming off the bench