Warren Buffett says that trimming his Apple stake was 'probably a mistake' - and Charlie Munger told him not to sell

• Warren Buffett said that trimming his Apple stake was a misstep.
• The Berkshire Hathaway CEO revealed that Charlie Munger warned him against selling.
• Munger was also against Berkshire's exit from Costco last year.
• See more stories on Insider's business page.

Warren Buffett said he was likely wrong to cash out some of his Apple shares last year.

"I sold some stock last year," the famed investor said at Berkshire Hathaway's annual meeting on Saturday. "That was probably a mistake."

Apple is by far the biggest holding in Berkshire's stock portfolio. Buffett's company has roughly tripled its money on the iPhone maker since investing $35 billion between 2016 and 2018.

Berkshire sold about $11 billion worth of Apple stock in the fourth quarter. Its stake is still worth north of $100 billion today.

Buffett revealed that his right-hand man and Berkshire's vice-chairman, Charlie Munger, told him not to sell Apple. Munger also advised him against exiting Costco, which has been his favorite company for years. Yet Berkshire sold its $1.3 billion stake in the big-box retailer in the third quarter of 2020.

The investor said that there are only so many things that Munger will let him get away with. "I used them up between Costco and Apple," he said.

Munger was "very likely was right in both circumstances." Buffett added.

The Berkshire CEO touched on many other topics during the meeting, including Berkshire's sale of the "big four" airlines and several bank stocks last year.