Uber boss Travis Kalanick plans to take time away from the company, and could return in a diminished role.
It comes after a review of management and practices at the firm, which is facing a number of scandals including complaints of sexual harassment.
Uber's board on Sunday voted in favour of the recommendations from the review.
Board member David Bonderman made a sexist remark at a meeting about the recommendations on Tuesday and has now resigned as a director.
In the email to staff, Mr Kalanick said the decision to take leave, which also comes after the sudden death of his mother in a boating accident, is part of an effort to create "Uber 2.0".
"For Uber 2.0 to succeed there is nothing more important than dedicating my time to building out the leadership team," he wrote. "But if we are going to work on Uber 2.0, I also need to work on Travis 2.0 to become the leader that this company needs and that you deserve."
Mr Kalanick's email did not say how long he would be away from the firm.
Analysis: Dave Lee, BBC North America technology reporter
When that blog post by former employee Susan Fowler dropped on a quiet Sunday afternoon in February, I doubt anybody at the company thought it would lead to this. I certainly did not.
That moment marked the beginning of the crisis at Silicon Valley's most talked-about start-up.
In the middle of it all, Travis Kalanick, a man who, rightly or wrongly, now symbolises what people feel is the very worst of tech "bro" culture. A man flush with money and an unrelenting ambition that slowed for no-one - until now.
Uber's problems were enough, most argued, for Mr Kalanick to make this decision. But coupled with the tragic death of his mother, the 40-year-old is quite understandably not in a position to give the company the attention it so desperately needs.
Since I started reporting this story I've been told how this problem is not limited to Uber; that it affects the tech industry far and wide. With that in mind, it will perhaps be encouraging to the rank-and-file at every tech firm that this fiasco began with one act: a woman brave enough to speak out.
Audio from a Tuesday meeting with employees to address sexism and other issues, leaked to a Yahoo News reporter, underscored how pervasive some of the problems appear to be.
Board member Arianna Huffington is heard saying the effect of having one woman on the board would be to likely to attract more women to it.
In response, Mr Bonderman - a founder of private equity firm TPG Capital and an Uber investor, reportedly responds: "It's much more likely to be more talking".
Mr Bonderman, who is a founding partner of private equity giant TPG Capital, later emailed staff to apologise, and then said he was stepping down from the board as of Wednesday.
He said he did not want his comments - which he said were "careless, inappropriate, and inexcusable" - to create a distraction for Uber as the company "works to build a culture of which we can be proud".
The ride-hailing company has been rocked by a series of controversies in recent months, including an investigation of its business practices and a lawsuit from Google's parent company, Alphabet, over alleged theft of trade secrets related to driverless cars.
Its corporate culture has been criticised for being aggressive, and this was inflamed earlier this year when Mr Kalanick was caught on video berating an Uber driver who voiced concerns about fares.
He said in response to the video: "I must fundamentally change as a leader and grow up."
His leave follows the departure of other high-level executives.
Uber last week also said it had fired more than 20 staff and taken action against others following a separate review of more than 200 HR complaints that included harassment and bullying.
It also emerged that the head of its Asia-Pacific business, Eric Alexander, had obtained the medical records of a woman who was raped by an Uber driver in 2014 and reportedly shared them with Mr Kalanick, senior vice-president Emil Michael and others.
Mr Alexander was fired earlier this month, while Mr Michael left Uber on Monday.
The recommendations released on Tuesday stem from a broader review conducted by the law firm Covington & Burling.
The proposed changes include starting performance reviews for senior leaders, reviewing the firm's pay practices, strengthening its HR department and seeking an independent chair for the board.
Liane Hornsey, Uber's HR chief, said: "While change does not happen overnight, we're committed to rebuilding trust with our employees, riders and drivers."