The announcement marked a U-turn for May, who had repeatedly said she would not seek an early vote.
After debating the motion put forward by May in Parliament, 522 of the 650 sitting MPs threw their support behind the early election, well and truly passing the threshold of two-thirds needed to approve the plan.
May wasted no time, going from the vote in Parliament to kick off her campaign with a speech in to supporters northwestern England.
Britain's most recent general election was in 2015 and before the April 19 vote, the next one was to have been held in 2020.
If approved by parliament, the election will be Britain's third general election in seven years, and it comes less than a year after the referendum that decided the United Kingdom would withdraw from the EU.
The SNP has signalled its MPs will abstain in the vote, but Labour and the Liberal Democrats have welcomed the early election.
Parliament will vote Wednesday on holding a June 8 election.
Labour leader Jeremy Corbyn said the election "gives the British people the chance to vote for a Labour government that will put the interests of the majority first".
After Mr Corbyn had addressed Labour MPs on Tuesday evening, a source close to the leader said the party was in for "the fight of our lives" but there was a "very positive mood" among his colleagues.
May announced on Tuesday her desire to take the country to the polls.
If current polling was replicated at the ballot box, the Tories would win an estimated 375 seats - nearly double the 189 that Labour would pick up. Ukip and the Lib Dems were both on 10pc.
Initially, EU officials had said that the talks could start in late May once a detailed negotiating mandate had been agreed among the EU's 27 other members.
In her interview with the Sun on Wednesday, Mrs May said "political game playing" risked hampering her Brexit negotiations, with some opponents "trying to stop us every step of the way".
The Prime Minister said she believed campaigning should be getting "out and about" meeting voters.
European Union officials say Britain's surprise election will not interrupt the bloc's preparations for Brexit talks - though they will slightly delay the start of negotiations. The leaders of the 27 remaining European Union countries will meet on April 29 to agree the bloc's negotiating position, which will then be translated into a legal text by the European Union commission in May.
"Following their conversation, the president considers that the real political negotiations on Article 50 with the United Kingdom will start after the elections foreseen for the 8th of June", the spokesman said, referring to European Union treaty rule that regulates the exit of a member state from the bloc. "She says it's about leadership, yet is refusing to defend her record in television debates".
And Plaid Cymru leader Leanne Wood - whose profile received a major boost from her involvement in two of the 2015 broadcasts - said: "Theresa May should be empty chaired if she doesn't show up to any planned TV debates".
"We need a general election and we need one now".
The source said Labour "was ready to fight it", but criticised the prime minister for what he called "her deceit of the country over calling the election".