Centre-right incumbent Marcelo Rebelo de Sousa had been widely expected to win another term with projections putting Socialist challenger Ana Gomes in second followed by far-right candidate Andre Ventura.
Portuguese media projections have shown President Marcelo Rebelo de Sousa winning his re-election after a poll affected by the country's virus lockdown.
Centre-right incumbent Marcelo Rebelo de Sousa had been widely expected to win another term.
The television station projections put Socialist challenger Ana Gomes in second followed by far-right candidate Andre Ventura.
Opinion polls had pointed to a first-round victory for Rebelo de Sousa, a former political commentator known for candid moments like queueing at the supermarket in shorts, plunging into the sea to help girls whose canoe had capsized or sharing a meal with homeless people.
Turnout reached 35.4 percent by 1600 GMT, only slightly lower than at the same time five years ago, soothing fears that abstentions might top 70 percent.
In the capital Lisbon, voters queued outside polling stations, being let in one by one under coronavirus social distancing rules.
"To those who can and who want to vote, overcome your fears", Rebelo de Sousa said after casting his ballot in Celorico de Basto, his stronghold in the northern region of Minho.
Another voter, architect Jose Barra, 54, told AFP: "Nothing would have stopped me from voting, but I think elderly people, for example, will be discouraged both by the virus and by the queues."
As mail-in ballots are not well-established in Portugal, early voting was available last Sunday, drawing nearly 200,000 voters.
Portugal has been under a second national lockdown for the past 10 days aimed at braking a surge in coronavirus cases.
The country recorded its worst daily coronavirus death toll on Sunday, bringing fatalities to almost 10,500.
More than 85,000 infections and almost 1,500 deaths were reported in the past week, the highest rate worldwide in proportion to its population of more than 10 million, according to an AFP tally based on government figures.
Almost every new day brings a fresh record in case numbers, and the government has now shut schools for two weeks on top of shops and restaurants.
Keep it to one round
The president has the power to dissolve parliament and call fresh elections -- a pivotal constitutional role with a minority government in power.
In his final campaign speech, Rebelo de Sousa -- often referred to simply by his first name -- urged voters to back him so as to avoid a second round.
That would "spare the Portuguese people from the election being stretched out over three crucial weeks" -- time that could be better spent slowing the pandemic, the former minister and co-founder of the centre-right Social Democratic Party (PSD) said.
"An abstention rate of 70 percent would be enough to make a second round almost unavoidable," the 72-year-old had warned.
Pre-election polls had given Rebelo de Sousa 58 percent of the first-round vote -- far ahead of Gomes and Ventura, on 15 and 10 percent.
A first-round re-election would fit in with Portugal's experience since adopting democratic government in 1974, with all four of the president's predecessors securing a second five-year term this way.
Rebelo de Sousa's popularity with voters has not suffered from his indulgence of Prime Minister Antonio Costa's socialist minority government.
He is so well-liked that the socialist party didn't even bother putting up a candidate, denying its backing to 66-year-old Gomes, a former diplomat and European lawmaker turned anti-corruption activist.
Meanwhile Ventura, the 38-year-old founder of right-wing populist party Chega -- "Enough" -- had said he was in the running to "crush the Left", which fielded three out of the seven candidates.
Portugal has so far to a large degree not seen the anti-establishment surges from the right that have reshaped the political landscape in many larger EU nations in recent years.
Ventura secured his party's first and only parliamentary seat at 2019 legislative elections, winning the backing of 70,000 voters or 1.3 percent.