The Archive in Nidzica is located in the center of the town in the old building named "Klasztorek" (Little Abbey). The building was founded in the 14th - 15th centuries in the south-eastern corner of the town walls. Through the ages the building served different functions in the town, not only military. There were stores, municipal school, school for lower church staff, library and cinema. The building was destroyed twice: during World War I and World War II. It was reconstructed in 1988.

This Branch Office of the Warsaw State Archives was founded in 1997. Its holdings contain records from other divisions of the Warsaw State Archives. There are mainly records of the administration of justice, court records, correctional administration records, notary records and also records of Warsaw co-operatives, institutions and state-owned companies, which were closed after 1989.