Castelo Branco is one of the 22 multi-member constituencies of the Assembly of the Republic, the national legislature of Portugal.

The constituency currently elects four of the 230 members of the Assembly of the Republic using the closed party-list proportional representation electoral system.

Castelo Branco currently elects four of the 230 members of the Assembly of the Republic using the closed party-list proportional representation electoral system.

Results of the 2011 legislative election held on 5 June 2011:[16] The following candidates were elected:[17] Carlos Costa Neves (PSD); Carlos São Martinho (PSD); Fernando Serrasqueiro (PS); and José Sócrates (PS).

Results of the 2009 legislative election held on 27 September 2009:[18] The following candidates were elected:[19] Carlos Costa Neves (PSD); Carlos São Martinho (PSD); Fernando Serrasqueiro (PS); and José Sócrates (PS).