The couple sent an e-mail to friends Friday announcing the news. They said they were looking at a possible wedding next summer. Matt McKenna, a spokesman for the former president, confirmed the engagement Monday.
Mezvinsky is a son of former Pennsylvania Rep. Marjorie Margolies-Mezvinsky and former Iowa Rep. Ed Mezvinsky, longtime friends of the Clintons. Ed Mezvinsky was released from federal prison last year after pleading guilty in 2002 to charges of bank and wire fraud.
Last summer, Hillary Clinton was forced to tamp down speculation that her daughter and Mezvinsky were already engaged and would marry in August on Martha's Vineyard. Those rumors proved to be false.
The couple became friends as teenagers in Washington and both attended Stanford University. They now live in New York, where Mezvinsky works at Goldman Sachs and Clinton is attending graduate school at Columbia University's School of Public Health.
After shunning the public spotlight for years, Chelsea Clinton became a fixture on the campaign trail during her mother's presidential bid in 2008, visiting colleges and universities around the country.