The valley of the Ipoly and especially the area of that around Szecseny was inhabited even in the prehistoric age. Findings attest that the region was peopled from the Neolithic period. Teutons, Avars, and Slavs appeared here in the first millennium BC.
Hungarians settled down in the surrounding country in the decades following the Hungarian Conquest, which began in AD 895. The town itself must have originated from that era. The burial places found on the confines of the town render this pretension probable.
The first genuine written document about Szecseny dates back to 1219. In 1334, Lord Chief Justice Thomas Szecsenyi induced King Charles Robert to permit the status of town, so Szecseny became a market town in the same year.
The Turkish occupied Szecseny in 1552 under the name "Secen" and after that the town became the center of a sanjak for several decades. The first Turkish occupation ended in 1593, whereupon Zsigmond Forgach became the landed proprietor of the town and the captain of the fortress at the same time. The second Turkish occupation lasted 20 years. Szecseny became practically deserted by the end of the nearly 150-year Turkish rule.
One of the most glorious parts of the town history is linked with the war of independence in 1703 that was called into being against Habsburgs by Prince Ferenc Rakoczi II. The Prince convened the Diet into our town in September 1705, where he was elected the ruling Prince of Transylvania and commander-in chief of the Hungarian insurgent forces. Although the war of independence failed, the inhabitants of the town still treasure the Princes memory. Many town institutions bear his name.
1737 is a remarkable date in the life of the town as the Forgach repurchased their property from Kohary family. The town began a slow development in the 18th century, a lot of private houses were built and the first pharmacy of the county was opened in 1741. The baroque style Forgach Castle - which is a museum nowadays - was built in that century as well.
The development of the town slowed down in the 19th century and fell behind other towns in Nograd, such as Balassagyarmat, Losonc, Salgotarjan. Szecseny lost its town status in 1886 owing to the decision of Parliament. In spite of the situation, a town hall was built in 1905 and the municipality organized a brilliant commemorative Rakoczi festival on the 200th anniversary of the 1705 Diet.
After the Treaty of Trianon in 1920, following the First World War, Szecseny became a frontier town, which has hindered its development until the present day. The Second World War did not keep out of Szecsenys way either. During the fighting raging in December 1944, the inhabitants suffered greatly.
After the conclusion of the war, the reorganization of life started immediately. Nationalization and collectivization brought fundamental changes in everyday life.
Until the end of the 1970s, Szecseny was an administrative center, being the chief town of the district. When the public administration system was reformed, the function of the seat of the district became extinct. As a result, several institutions and offices were closed down, e.g. the district court, the title registry, the central police station, and the high school. Two other settlements belong to Szecsenys current administration, though: Postenypuszta, located beside the River Ipoly, and Benczurfalva, 4 kilometres (2 miles) away.
The recession in the 1990s also damaged the local economy, but significant improvements in infrastructure were carried out, including sewer and gas networks and connection to the national telephone network.
The institutions of the town also have changed. A second high school was founded in 1994, along with an ambulance station and nursing home. The agricultural vocational school and the art school, though, were transferred to the county seat.