	In each group, teams played against each other home-and-away in a round-robin format. The group winners and runners-up advanced to the round of 16, while the third-placed teams entered the 2017–18 UEFA Europa League round of 32. The matchdays were 12–13 September, 26–27 September, 17–18 October, 31 October – 1 November, 21–22 November, and 5–6 December 2017.