[9] Dortmund were also the German club involved in the biggest transfer of the summer, selling young French forward Ousmane Dembélé to Barcelona for an initial €105 million.
[10] Meanwhile, reigning champions Bayern Munich prepared for the season by breaking the league's transfer record in their purchase of French midfielder Corentin Tolisso from Lyon for €41.5 million.
[15] In the January 2018 transfer window, Dortmund lost the season's second-top scorer, Gabonese forward Pierre-Emerick Aubameyang, who moved to Arsenal for a €63 million fee.
[17] From December to February, Bayern went on a 10-match winning streak that ended with a goalless draw with Hertha BSC at the Allianz Arena,[18] and managed 13 unbeaten until a 1–2 loss at Leipzig on 18 March.
[21] Bayern won their 27th Bundesliga and 28th German title (6th consecutive) on 7 April 2018, with five games left to play after defeating fellow Bavarian club FC Augsburg 4–1.
[23] On the last matchday, 1899 Hoffenheim beat Dortmund 3–1 to finish ahead of the latter on goal difference at an all-time high third place and securing a spot in the Champions League group stage for the first time in their history.