[1] Like most of Europe, until the Middle Ages the defence of public order was the responsibility of local communities, under the authority of feudal lords and courts.

[2] The first corps of police agents, the Quadrilheiros, was created by Fernando I, on 12 September 1383, consisting of 20 members, who were recruited by force from the strongest physical men, to serve Lisbon.

[2] These men were subject to the town council for three years, and required to swear fealty and carry a weapon (a staff), which they would display at their homes, representing a symbol of their authority to arrest and direct criminals to the Corregedores (magistrates).

King John IV of Portugal provided a new charter, and a decree on 29 November 1644, forced them (under terrible sanctions) to serve the public, working in the day and evenings.

[2] Sebastião José de Carvalho e Melo, the Marquess of Pombal, found it necessary to create an organism to centralize all laws.

The first Quartermaster-General was Inácio Ferreira Souto, at the same time that the term polícia (police) was commonly used, and the Quadrilheiros were relegated to the evenings.

However, this foundation did little to resolve criminal issues, and locks on doors, grades on windows and blunderbusses beside the bed continued to be important.

[2] Instructed in laws at the University of Coimbra, he became a powerful chief: he began by expunging the police services of criminal elements, and took advantage of all laws to arrest all criminals or suspects in the Alfama, Mouraria, Bairro Alto and Madragoa, reorganizing the services and bringing a level of respectability to the department.

[2] Around the same time, the Guarda Real de Polícia (Police Royal Guard) was founded on 25 December 1801, a militarized cavalry corps.

[2] The police prerogatives of this position remained temporary and territorial, influenced by prefects, general administrators and later civil governors.

[2] To remedy this situation, King Luis ordered the publication of a law that founded a corps of civil police (2 July 1867).

[2] In July 2024, the PSP assisted French law enforcement by sending officers to Paris to protect the city for the Olympics with National Republican Guard troops.

The access to the agent category requires the conclusion of a technical course in the Practical School of Police (EPP) at Torres Novas.

The various categories, ranks, insignia and respective main functions are: Since 2004, the Skoda Octavia has been the principal model of patrol car used by the Public Security Police.

Single apprehended Audi R8, BMW i8, Porsche 996 Turbo and Subaru Impreza Prodrive are used as special pursuit cars.

Ground speed radar equipped Toyota Avensis and Volkswagen Sharan minivans are used for traffic enforcement, such as some Audi A4 3.0 TDI and Bmw 335i unmarked patrol cars, while some Toyota Hilux pickup trucks and Land Rover Defender jeeps are used for patrolling non urban and mountainous areas.

A huge number vans are also in service, including newer Mercedes-Benz Metris and Sprinter (with flip down wire shield across the windscreen) and Citroën Berlingo to prisoners transport.

For the traffic patrol vehicles there is a variant, which intermediates red stripes with the blue ones and has the wording "TRÂNSITO" (transit) on the rear side panels.

Another variant of the livery is its negative version (blue, with the stripes and wording in white) to be applied in vans and special vehicles.