Valga is bounded on the north by the municipalities of Dodro, Pontecesures, and Padrón; to the south by Catoira and Caldas de Reis; to the east by Cuntis; and to the west by Dodro.

Located on the left bank of the lower course of the Ulla River, it is crossed by the AP-9 motorway, the Vigo-A Coruña railway line, the N-550 from A Coruña to Pontevedra, and the PO-548 from Pontecesures to Vilagarcía.

The northern part of the territory is occupied by the broad valley of the Ulla River, where the Louro and Valga rivers flow, running parallel for part of their course. To the south, there are two hills, Mount Xiabre and Mount Xesteiras. Communication routes run through the depression formed between these two spurs.

Temperatures are mild, with an average of 13 °C. Rainfall is abundant, reaching 1,700 mm per year.