"We bought more stocks by a considerable margin than we sold in the first quarter," Buffett told CNBC's Becky Quick in an interview that aired on Friday.
Buffett pointed out that he's usually a net-buyer of stocks in the first quarter, but he stressed the "considerable" part this year.
He said Berkshire's newly revealed purchase of 75 million Apple shares during the first quarter, which added to the conglomerate's already massive stake in the tech giant, "brought down our cash position moderately."
The stock market since January has been on a wild ride.
The Dow Jones industrial average and the extended their strong 2017 rallies to start off the new year, hitting record highs on Jan. 26. But then stocks hit a brick wall, dipping in and out of correction territory since then.
Year to date, as of Thursday's close on Wall Street, the Dow was down 3.2 percent. The S&P 500 was down 1.6 percent so far in 2018.
Buffett spoke to CNBC on Thursday evening from Omaha, Nebraska, where tens of thousands of Berkshire shareholders were gathering for Saturday's annual meeting.