Kimmich played in the 2017 DFL-Supercup and won the title as Bayern defeated their arch-rival Borussia Dortmund on 5–4 penalties after the extra time ended 2–2. On 16 September, he provided overall three assists to Thomas Müller, Arjen Robben and Robert Lewandowski's goals to defeat 1. FSV Mainz 05 with a 4–0 victory. On 9 March 2018, Kimmich signed a three-year contract extension which lasts until 30 June 2023. He managed to score each goal in both the first and second leg in the Champions League semi-final tie against Real Madrid, but his side were knocked out from the competition on 4–3 aggregate. Kimmich finished the 2017–18 season with six goals and seventeen assists in 47 appearances.