Badenoch, who is the sixth Tory leader in less than nine years, now faces the task of uniting a fractured party and leading opposition to Sir Keir Starmer’s Labour government.
The Saffron Walden MP said the Conservatives need to “bring back” voters who abandoned them, adding: “Our party is critical to the success of our country.
“But to be heard, we have to be honest.”
The party must admit it “made mistakes” and “let standards slip” over the last 14 years in government, she said.
Badenoch chose not to set out detailed policies during her campaign, focusing instead on returning the Conservatives to “first principles”.
All eyes will now turn to who she appoints to her top team as she sets out the future shape of the party over the coming days.
She praised Jenrick despite a sometimes bruising campaign and hinted he may be offered a senior job, telling him “you have a key role in our party for years to come”.
Badenoch, who became an MP in 2017 after a career in banking and IT, has said she would offer jobs to all of the Tories who launched leadership bids in July.
But shadow home secretary James Cleverly, who came third in the race, has ruled himself out.
The BBC understands, Badenoch plans to reveal her shadow cabinet by Wednesday, ahead of the critical Budget vote and her debut clash with Sir Keir at Prime Minister’s Questions.
Jenrick did not speak to reporters after the result was announced, but on social media, external called on his supporters “to unite behind Kemi and take the fight to this disastrous Labour government”.
He also thanked “everyone who supported my vision for a Conservative Party rooted in the common ground of British politics”.
Badenoch got 53,806 votes to Jenrick’s 41,388 – making it the closest Tory leadership race of recent times.
Bob Blackman, who oversaw the election as chair of the Conservative 1922 Committee, revealed the party membership had shrunk to 132,000 – the lowest level on record and down 40,000 members since the last vote by members in 2022.