The result was revealed by Nationals whip Michelle Landry, who did not disclose how many of her colleagues voted for each candidate.
"We're not revealing numbers," Ms Landry told reporters in the corridor outside the party room.
The Nationals whip would not comment in detail on the leadership pitch made by George Christensen, who has recently suggested the regional party consider leaving its Coalition partnership with the Liberals.
"George is passionate about the National party ... it's his democratic right to get up in the partyroom and speak," she said.
"George decided that he wanted to stand up and talk about the National party values."
"I bought myself a new whip this week to keep the boys in line in the party room."
Prime Minister Malcolm Turnbull congratulated his new deputy as they posed together for TV cameras shortly after the appointment.
"The Liberal Party has been in partnership with the Nationals for all of its life," Mr Turnbull said.
Mr McCormack said the Coalition partnership would continue "long into the future".
Christensen run a surprise to Nats expecting unity ticket
Deputy Nationals leader Bridget McKenzie had urged a consensus approach, asking the Nationals to rally behind a single candidate.
Michael McCormack was expected to be the only candidate after NSW MP David Gillespie withdrew from the race on Sunday afternoon.
There had been some speculation that Agriculture minister and staunch Joyce supporter David Littleproud could run, but confirmed he would not contest the ballot late on Sunday night.
Newly elected leader Michael McCormack said the challenge from his "mate" George Christensen would not damage the unity of the party.
"I congratulate George for putting his hand up," he said, briefly putting his arm around his Nationals colleague.
"That's the National Party. We talk openly about things with each other."
George Christensen released a statement offering his congratulations to the new leader.
"I expressed my views on the need to change the current political direction the Nationals are moving in, in a Facebook post over the weekend," Mr Christensen wrote in a statement.
"My colleagues did not agree with my views, and that’s democracy."
Nationals seek changes in cabinet reshuffle
Mr McCormack was sworn in as deputy PM at Government House just a few hours after his election, where he also officially took over Barnaby Joyce's former roles as minister for Infrastructure and Transport.
The new deputy will soon meet with Prime Minister Malcolm Turnbull, fresh off a plane from his recent official visit to the United States, to discuss an imminent cabinet reshuffle.
Both Liberal and Nationals members have suggested any redistribution will probably be minor.
But the Nationals are pushing for the Small Business portfolio, once held by Mr McCormack, to be elevated to a cabinet-level ministry.
Nationals senator John Williams said he would like to see the Regional Development ministry, currently held by Liberal John McVeigh, handed over to Nationals representation.