[3] The municipality consists of one freguesia (civil parish), Santa Catarina.

The freguesia is subdivided into the following settlements (population data as of 2010[update]):[1] The municipality of Santa Catarina has a rugged relief, characterised by steep slopes that border the river valleys, rocky peaks and volcanic cones.

Its mountains, including Serra Malagueta and Pico da Antónia, are the highest of the island.

[5]: 19  Santa Catarina borders Tarrafal to the north, São Miguel to the northeast, Santa Cruz to the east, São Salvador do Mundo to the southeast and Ribeira Grande de Santiago to the south.

[5]: 19 [6] Initially, its seat was the new town of Picos, between 1859 and 1869 it was Achada Falcão (Cruz Grande), between 1869 and 1912 Tarrafal, and since 1912 Assomada.