Are there mosquitoes in Lisbon? Yes, mostly at night through an open window.

Yes, mostly the common house mosquito, which bites at night through open windows from about May to October. A newer arrival, the Asian tiger mosquito, a daytime biter, has turned up in a few neighborhoods since 2023. No locally acquired mosquito-borne disease has been reported in Lisbon, so a summer trip needs little more than an evening repellent and a closed window.

Night bites through an open window

The house mosquito, Culex pipiens, is the most common mosquito in every region of Portugal. It bites at night from about May to October, with a peak in July and a second one in October, and it gets in through open windows. Hot, still nights with the windows open bring the most bites. Close the windows before you switch on the lights in the evening, use the air-conditioning if the room has it, and run a plug-in vaporizer, sold in any supermarket or farmácia. On a terrace, one coat of repellent at dinner covers the evening. Many Lisbon residents on forums say bites are rare, though a single mosquito in an unscreened bedroom can still cost you sleep.

The greener hills outside the city draw more complaints. Country houses in the Sintra hills, near Colares and Cabo da Roca, tend to get heavier biting, with woods and vineyards all around. Ask whether your room has screens before you book.

The tiger mosquito arrived in 2023

The Asian tiger mosquito, a daytime biter, was first found in Lisbon in late September 2023 at three sites: Algés in Oeiras, just west of Belém, and the Alvalade and São Domingos de Benfica neighborhoods. Their genetic signatures differed, so researchers at INSA, Portugal's national health institute, concluded they were three separate introductions in a single season, the Alvalade one possibly from the Algarve. By 2025 the species had been recorded in at least 28 mainland municipalities, including Almada and Sesimbra across the Tagus. Portugal's health authority, DGS, rates its presence at level 1 (yellow) on a 0-to-3 scale.

On September 24, 2026, a trial released 30,000 sterile male tiger mosquitoes in Alvalade, the last batch of its first phase. Males don't bite, and wild females that mate with them lay eggs that never hatch, so repeated releases should shrink the local population. In the city the species is still patchy. Where it is around, it bites in gardens and on terraces, mainly in the morning and late afternoon, so put repellent on before a garden visit or a long terrace lunch. It stays active into November, so a fall trip still calls for it.

No local disease

Local transmission of the viruses the tiger mosquito can carry, such as dengue and chikungunya, has not been detected on the mainland, INSA researchers wrote in 2024, and the European Centre for Disease Prevention and Control's 2026 reports, to October 21, list local dengue only in Italy and France. West Nile shows up in Portugal mainly in horses. In 2026 the country reported 4 outbreaks in horses, in the Setúbal peninsula, the Lezíria do Tejo and the Alto Alentejo, none in Greater Lisbon, and there were no human cases in 2025 or 2026.

CDC's Portugal page lists no malaria medicine, and the yellow fever vaccine is neither recommended nor required. Under diseases spread by bugs it lists only leishmaniasis, spread by sand flies that bite from dusk to dawn, which your evening repellent covers.

Where you're staying

Here is how the city and the day-trip country around it compare for a June–September trip.

The Portugal briefing covers the whole country, from Porto to the dog-and-sand-fly question. Heading south? Our Algarve briefing covers the coast and its lagoons.

What travelers report

Paraphrased from a TripAdvisor thread and two country-house reviews and linked so you can read them in full. Only the Belém thread is dated, and bites vary with the weather and whether your room has screens.

• Belém, Lisbon · late summer · 2026

  A traveler staying in Belém posted that they were being bitten alive. Replies said it takes only one mosquito slipping in through the window to spoil a night and that plug-in repellents are sold locally. TripAdvisor ↗

• Quinta Vale da Roca, Azoia (Sintra)

  A couple in a sea-view room said mosquitoes bit them heavily on both nights, with more than 20 bites each on their faces after the first, and blamed the time of year and wet weather. The hotel replied that it treats the buildings regularly but that the surrounding nature and vineyards make mosquitoes more noticeable in some weather. TripAdvisor ↗

• Quinta Colina Flora, Colares (Sintra) · before the main season

  A guest had to keep all the windows closed because of mosquitoes, which made the cottage stuffy. The owner apologized that the mosquito screens had been taken down for cleaning because the season had not started, and said they had since been replaced. TripAdvisor ↗

One rule outlasts the trip. Any fever during or after your trip means a doctor visit, and you tell the doctor where you were.

Traveler questions