Kairouan is about 160 km south of Tunis and 60 km west of Sousse. There is no train service to Kairouan. The most practical way to arrive is by bus from Tunis (around two and a half hours, SNTRI services from Bab Bhar/Bab Saadoun terminal) or from Sousse (around ninety minutes). Louages (shared long-distance taxis) also run from both Tunis and Sousse and are faster if you get a full car.
By car, Kairouan is easily reached via the GP2 motorway from Tunis or via the P1 road from Sousse. Parking is straightforward on the edge of the medina. The drive from the coast makes Kairouan a feasible long day trip from Sousse or Monastir, though an overnight stay lets you see the Great Mosque at dawn and the medina in the early morning before tour groups arrive.