LVMH announced it was buying Tiffany & Co. for $16.2 billion, or $135 per share in cash on Nov. 24.
Tiffany will join iconic brands including Louis Vuitton, Givenchy and Celine under the LVMH umbrella.
LVMH is not required to hold a vote of its stockholders to approve the Merger Agreement.
The company anticipates that the merger will be completed in the middle of 2020.
Its chairman, Bernard Arnault, joined Amazon CEO Jeff Bezos and Microsoft founder Bill Gates as the only people in the world worth more than $100 billion in June.
Buffett apparently made the decision as his holding company, Berkshire Hathaway, goes on its fourth year without making a significant acquisition despite its $128 billion cash on hand.
LVMH offered Buffett the chance to make a counteroffer, but he declined, The Financial Times reported citing those who know the circumstances.
Buffett confirmed to the Times that LVMH approached him with the opportunity.
Fox Business' Audrey Conklin and Edie Fordham contributed to this article.