Soutomaior is about 20 km south of Pontevedra and 20 km northeast of Vigo in the Ría de Vigo valley. By car, take the AP-9 motorway (the main Vigo–Pontevedra road) and exit at Arcade/Soutomaior; the journey from either city takes around 20 minutes. The castle is well signposted from the motorway exit.
By public transport, local buses connect Soutomaior with Pontevedra and with Arcade (the nearest village on the Pontevedra side). The bus stops in the town centre, about a 15-minute walk from the castle. There is no train station in Soutomaior itself; the nearest stations are at Arcade and Redondela on the Vigo–Pontevedra line. Most visitors come by car, as the castle and gardens are the primary reason to visit and there is little else in the immediate area.
The combination of Soutomaior with Pontevedra — one of the best-preserved historic town centres in Galicia, just 20 km north — makes a natural day trip from Vigo.