MacKenzie Bezos announced on Tuesday that she had joined the philanthropic effort known as the Giving Pledge, in which participants promise to give away more than half of their wealth during their lifetime or in their will.

Following her divorce from Amazon's founder, Jeff Bezos, earlier this year, MacKenzie Bezos received a stake in the retail giant that puts her net worth at almost $37 billion, according to Amazon's latest share price.

"We each come by the gifts we have to offer by an infinite series of influences and lucky breaks we can never fully understand," Bezos wrote in her letter. "My approach to philanthropy will continue to be thoughtful. It will take time and effort and care. But I won't wait. And I will keep at it until the safe is empty."

Read more: Jeff and MacKenzie Bezos have finalized the terms of their divorce — and she's set to come out of it as one of the richest women in the world

The Giving Pledge, started almost a decade ago by Warren Buffett and Bill Gates, is signed by some of the wealthiest families and people in the world. Other tech billionaires who have joined the pledge include Mark Zuckerberg and Priscilla Chan, the Airbnb cofounder Brian Chesky, and the LinkedIn cofounder Reid Hoffman.

Notably, the world's richest person has refused to sign on to the Giving Pledge: Jeff Bezos, who has a net worth of $114 billion, is the only American ranked in the top five on the Bloomberg Billionaires Index of the world's richest to not join on to the charitable pledge. His latest effort to give away to charity was a $2 billion donation in September, which reportedly represented about 1.3% of his net worth at the time.

Still, Jeff Bezos praised his his ex-wife on Tuesday for her Giving Pledge commitment.

"MacKenzie is going to be amazing and thoughtful and effective at philanthropy, and I'm proud of her," Bezos said on Twitter. "Her letter is so beautiful. Go get 'em MacKenzie."

The Bezoses announced in early April that they had finalized the terms of their divorce. Under the agreement, MacKenzie Bezos granted the Amazon CEO all her interests in The Washington Post and Blue Origin, as well as 75% of the Amazon stock they owned and voting control over the shares she retained.

The terms of the divorce left MacKenzie Bezos with a stake in Amazon worth almost $37 billion, placing her in the top five among the world's richest women.

MacKenzie Bezos was one of the first employees at Amazon, and she has written two award-winning novels. MacKenzie and Jeff Bezos had four kids over their 25-year marriage.