[11] On 15 August 2015, Brandt scored the winning goal after appearing as a substitute in a 2–1 victory against 1899 Hoffenheim in Bayer's opening match of the 2015–16 Bundesliga season.

[13] On 26 August 2017, Brandt became the youngest-ever Leverkusen player to reach 100 Bundesliga appearances, doing so at the age 21 years, three months and 25 days during a 2–2 draw against Hoffenheim.

[14] During the second half of the 2018–19 Bundesliga campaign, Brandt was re-positioned by new club manager Peter Bosz, shifting from his natural wide position to a more central role in midfield alongside Kai Havertz.

[21] Brandt scored his first Bundesliga goal for Borussia Dortmund in his first match on 17 August, a 5–1 against FC Augsburg on the first matchday, coming on as substitute for Thorgan Hazard.

[25] His performance improved in subsequent seasons, contributing significantly to Dortmund's offense and securing a DFB-Pokal win and a runner-up finish in the 2022–23 Bundesliga.

[30] On 17 June, Brandt made his first World Cup appearance as a substitute by replacing Timo Werner in the 86th minute in the opening match against Mexico in which they lost 1–0.