Clinton spokesman Matt McKenna confirmed Chelsea Clinton, 29, likely got engaged to Mezvinsky sometime before Thanksgiving, ABC News reported Monday.
The couple sent out an e-mail last Friday announcing their engagement and a possible wedding date for next summer.
"We're sorry for the mass e-mail but we wanted to wish everyone a belated Happy Thanksgiving! We also wanted to share that we are engaged! We didn't get married this past summer despite the stories to the contrary, but we are looking toward next summer and hope you all will be there to celebrate with us," the couple said.
Chelsea Clinton, daughter of U.S. Secretary of State Hillary Clinton, began dating Mezvinsky, son of former U.S. Rep. Ed Mezvinsky, D-Iowa, and former U.S. Rep. Marjorie Margolies-Mezvinksy, D-Pa., in 2005.
ABC News said Clinton and Mezvinsky were childhood friends whose friendship intensified while they were attending Stanford University.