After Jan. 1 and before Apple reported earnings on Jan. 31, Buffett's Berkshire Hathaway added almost 76 million Apple shares to its holdings. Asked why, he said, "Because I liked it!"
The purchases that Buffett revealed on Monday give Berkshire Hathaway about 2.5 percent outstanding Apple shares. It also makes Apple one of Buffett's company's largest holdings, second only to Coca-Cola.
At this point, Buffett owns $17 billion worth of the tech giant's stock. The legendary investor said he upped his stake because of the consumer-retaining power of Apple and CEO Tim Cook's smart capital deployment strategy.
"Apple strikes me as having quite a sticky product, and an enormously useful product to people that use it," Buffett told CNBC.
The Berkshire Hathaway chairman and CEO said that late investor Philip Fisher's 1958 book "Common Stocks and Uncommon Profits" inspired him to research how consumers feel about Apple products.
"He talks about something called the 'scuttlebutt method,' which made a big impression on me at the time, and I used it a lot," Buffett said. "[It's] essentially going out and finding out as much as you can about how people feel about the products that they [use.]"
And, while the results were favorable enough for Buffett to greatly up his stake in Apple, "I don't have an iPhone," the investor said. "I have an iPad. Somebody gave it to me though."
Still, when asked which company he thinks is most likely to reach a $1 trillion valuation first between Apple and his own Berkshire Hathaway, Buffett said he'd put his money on Apple.
"I'd bet on Apple just because they've got a stronger position," the investment guru said, joking that if Cook wanted to swap positions, Buffett would be open to a deal.
Apple stock was slightly higher in premarket trading Monday.
Correction: This story was revised to correct that it was Buffett's Berkshire Hathaway that purchased 76 million shares of Apple in January.