Mr Trudeau announced the election for September 20 after visiting the governor general, who holds a mostly ceremonial position representing Britain’s Queen Elizabeth II as head of state.
“We’ve had your back and now it’s time to hear your voice,” Mr Trudeau said. “Canadians need to choose how we finish the fight against Covid-19.”
His Liberal Party fell just short of a parliamentary majority two years ago and must rely on the opposition to pass legislation.
He is not as popular as he once was, but his government’s handling of the pandemic has been widely regarded as a success.
After a slow start, Canada now has enough vaccine for every citizen.
More than 71 per cent of eligible Canadians are fully vaccinated and over 82 per cent have received at least one dose.
The government has spent billions to prop up the economy amid lockdowns that have now been lifted.
But if the result is another minority government, the “knives will start to come out", said Robert Bothwell, a professor of Canadian history and international relations at the University of Toronto.
“Mr Trudeau is not widely liked," Prof Bothwell said. "He’s what the Liberals have so they will fall in behind him, but if he loses he’s toast.
“It’s not that he’s unpopular but there’s no affection there. The Liberals behave as if he is this beloved figure but he’s not. The novelty is gone.
"But there’s still enough there and the performance on Covid was pretty solid, so I think people will balance these things going into the election and vote for Trudeau.”
Mr Trudeau, son of the late Liberal prime minister Pierre Trudeau, became the second youngest prime minister in Canadian history when he was elected with a majority in Parliament in 2015.
His victory ended almost 10 years of Conservative Party government in Canada, but scandals and high expectations have damaged his standing.
Mr Trudeau's father was prime minister from 1968 to 1984, with a short interruption.
Opposition leftist New Democratic Party leader Jagmeet Singh said it was “selfish” for Mr Trudeau to call an election during a pandemic.
Ontario, Canada’s largest province, on Sunday reported more than 500 cases for the fourth straight day.
Opposition Conservative leader Erin O’Toole did not answer when asked if his candidates would or should be vaccinated.
Mr O'Toole said he was disappointed that Mr Trudeau was trying to divide people about their health.
“The Liberals are going to keep pounding the Conservatives on this and it will happen as the fourth wave of the pandemic is picking up steam," said Nelson Wiseman, a political science professor at the University of Toronto.
”The fourth wave could hurt the Liberals if lockdowns are reimposed.”
Prof Wiseman said many Canadians would resent having an election they consider to be unnecessary but the Liberals would win the most seats.
“Trudeau is seen as having delivered on vaccines and there has been widespread support for the government’s income-and job-support programmes to counter Covid’s economic fallout,” he said.
“Canadians compare their situation to the US. The current spike in the US contributes to smug complacency among Canadians. This feeling benefits the Liberals at present.”
Mr Trudeau began his briefing on Sunday by talking about the Taliban’s takeover of Afghanistan.
Canada closed its embassy in Kabul and staff have fled the country.
“The current situation poses serious challenges to our ability to ensure the safety and security of our mission,” Mr Trudeau said.
Canada has committed to taking in 20,000 refugees from Afghanistan and Afghans who have assisted Canada over the years.