TAP Air Portugal was founded as a division of Portugal's Civil Aviation Department under the name Transportes Aéreos Portugueses on 14 March 1945, and started operations on 19 September 1946, initially serving the Lisbon–Madrid route using the Douglas DC-3.^: 917 A year later, the carrier added a route to Angola and Mozambique, at the time claimed to be the world's longest route operated with a DC-3, having 13 intermediate stops.^: 838

In 1957, the airline deployed Super Constellations on the Lisbon–London and Lisbon–Paris sectors, yet operations of the type date back to November 1955 (1955-11), when these aircraft started flying the route that linked Portugal with Portuguese Angola and Portuguese Mozambique.^: 917 By December 1957 (1957-12), the carrier's network consisted of the long-haul Lisbon–Kano–Leopoldville–Luanda–Lourenço Marques route, as well as medium- and short-haul routes radiating from Lisbon and serving Casablanca, London, Madrid, Paris and Tangier, and a single domestic flight between Lisbon and Oporto.^: 917 On 1 November 1962, the airline started services between Lisbon and London, flying the route using the Sud Aviation Caravelle, taking over the services that had been operated by British European Airways on behalf of the company.

As of August 2012, TAP Portugal was the European airline with the most destinations in Brazil (10), being the leader in terms of passengers transported between this country and Europe, in comparison with their European counterparts, as well as with the Brazilian ones. As of August 2012, the airline was the third largest to serve Latin America by number of passengers; as of March 2013, the carrier shifted to the fourth place in the Europe-Latin America sector. Data from the latest financial report, corresponding to the fiscal year 2012, showed that the airline had its main source of traffic in Europe, and their most important long-haul market was South America.

Apart from Brazil, the countries with the most destinations served by the carrier are Spain (7), France (6) and Germany (5). TAP Portugal also flies to other 25 international destinations in Europe, 15 in Africa, two in the United States and one more in Latin America (Caracas). In the end of 2013, TAP announced its plan to start flying to six additional destinations in Europe during 2014 (Nantes, Hannover, Tallinn, Gothenburg, Belgrade and Saint Petersburg), whose schedule was announced prior to 31 March 2014. As of June 2014, the number of destinations in Brazil served by the carrier increased to 12 with the addition of Belém and Manaus to the route network. During July 2014 (2014-07), TAP Portugal launched services to Belgrade, Bogotá, Gothenburg, Hanover, Nantes, Oviedo, Panama City, Saint Petersburg and Tallinn.