It shares borders with Slovakia and the Hungarian counties Pest, Heves and Borsod-Abaúj-Zemplén.

Nógrád is famous for its historic architecture of ancient Gothic churches and stone castles dated to the 13th century.

Some historic landmarks includes the Salgó Castle and several baroque buildings constructed in the 18th century and the Vay, Teleki.

The mountain ranges Börzsöny, Cserhát and Mátra lie partly in the county.

The two largest settlements are Balassagyarmat, the former county seat, and Salgótarján, which has become a center of industry in the early 20th century due to coal mines nearby.