Warren Buffett's 'Mystery Stock' Revealed in New Filing
Warren Buffett’s multinational holding company Berkshire Hathaway has unveiled the “mystery stock” that had been kept hidden in previous financial results, ending months of speculation about the latest investment bet from the “Oracle of Omaha.”
A holding Barron’s had valued at $4.8 billion was granted “confidential treatment” in recent quarterly filings with the U.S. Securities and Exchange Commission (SEC).
A 13-F report published on Thursday revealed that multiple investments comprised this “mystery stock,” and that Berkshire had been building up stakes in steelmaker Nucor, as well as homebuilders Lennar and D.R. Horton.
Why It Matters
Buffett is among the most followed and revered investors in the world, given the staggering and market-beating returns Berkshire Hathaway has delivered during his six-decade tenure leading the conglomerate. As a result of this track record, Buffett’s investments are often interpreted as a vote of confidence in a company’s underlying strengths and its potential for strong returns.
What To Know
According to Thursday’s filing, as of June 30, Berkshire held around 7.2 million shares of Lennar, 6.6 million of Nucor and 1.5 million shares of D.R. Horton, thanks to purchases made over the past two quarters. Following the report, all three companies saw noticeable upticks in their share price in after-hours trading.
The logo of Berkshire Hathaway Inc. is displayed on a smartphone screen on May 11, 2025, in Chongqing, China.
Photo illustration by Cheng Xin/Getty Images
Lennar is one of the largest homebuilders in the U.S. and often viewed as a bellwether of the wider U.S. housing market. The stock is up around six percent in the year-to-date. Fellow homebuilder D.R. Horton is up around 20 percent. Meanwhile, North Carolina-based Nucor, a leading American steel producer, is up roughly 27 percent in 2025.
Together, these investments were worth around 1.8 billion as of June 30, according to analysis by Barron’s.
In addition to these, Berkshire disclosed that it had purchased five million shares of embattled insurer UnitedHealth, acquiring a stake valued at approximately $1.6 billion. Beyond the high-profile assassination of CEO Brian Thompson last December, the company has also been grappling with a succession of financial difficulties.
In late July, UnitedHealth reported that its earnings from operations had dropped to $5.2 billion in the second quarter from $7.9 billion for the comparable period in 2024, though revenue rose to $111.6 billion from $98.9 billion. The stock has fallen around 40 percent in the year-to-date, though it was up over 13 percent as of noon ET on Friday following Berkshire’s stamp of approval.
As well as Berkshire, CNBC reports that famed investor Michael Burry, known for his prophetic bets against the housing market ahead of the 2008 crash, has also built up a sizable stake in the company.
During the second quarter, Berkshire also sold 20 million shares of Apple and 26 million shares of Bank of America, both among its biggest holdings, as well as its entire stake in T-Mobile.
What People Are Saying
UnitedHealth CEO Stephen Hemsley, during an earnings call last month, said: “We have the chance to reposition our enterprise as a far more modern, reliable, consumer and provider friendly enterprise using new technologies and approaches, and we are going to pursue that course. Pursuit of these opportunities aligns to and enables our reform and change mandate and allows us to better achieve our mission and to steadily perform better in doing so.”
Aswath Damodaran, professor of corporate finance and valuation at the Stern School of Business at New York University, told Newsweek he believed the recent investment were likely decisions made by other Berkshire executives.
“If you think Warren Buffett is immersing himself in the finances and politics of health insurance at the age of 93, I think that you have a very different vision than I do,” he said.
What Happens Next
Buffett will be stepping down as Berkshire’s CEO at the end of this year. In May, he announced that Greg Abel, vice chair of noninsurance operations, would be taking over the role, but that he would remain chairman of the company’s board of directors.