Mr. Hudak, 41, became the party's 21st leader following a convention on Saturday in Markham, Ont.
Mr. Hudak won 5,606 votes on the third ballot. He needed 5,125 to win.
He was in a two-way race with Frank Klees following the second ballot.
"Our party stands united to say, 'Dalton McGuinty, your days are numbered," Mr. Hudak said in his victory speech.
"Ladies and gentlemen, I am honoured and humbled by the trust you have placed in me."
Mr. Hudak, 41, received 3,511 electoral votes on the first count while Mr. Klees was nipping at his heels with 3,093 votes.