Agadão was created when the religious parish was de-annexed from Castanheira do Vouga, to establish a new faith community.

The lands of the parish later pertained to the Counts of Feira, until the last Count Fernando Forjaz Pereira Pimentel de Menezes e Silva died in 1700 without an heir, and those lands were transferred to the Casa do Infantado (that included several seigneurial holdings confiscated from the Spanish after the Portuguese Restoration War).

It contains the localities Alcafaz, Bertufo, Boa Aldeia, Caselho, Corga da Serra, Felgueira, Foz, Guistola, Guistolinha, Lázaro, Lomba, Lousa, Povinho, Sobreira and Vila Mendo.

In addition to agriculture, the forestry sector and industry are the dominant economic activities in the local villages.

The parish's gastronomic specialties include chanfana (a rich lamb stew cook in a cast-iron pot slowly for 5 hours) and broa de milho (a traditional bread made from corn and wheat flour).