Apple (AAPL 2.48%) is the largest stock investment in Berkshire Hathaway's (BRK.A -0.23%) (BRK.B -0.28%) closely watched stock portfolio, and it isn't even close.

At the end of 2023, Berkshire Hathaway owned 905,560,000 shares of the iPhone maker, and as of April 15, this translates to a market value of approximately $156 billion. Berkshire Hathaway's investment represents 5.9% ownership of Apple, making up about 43% of Berkshire's portfolio. For context, Berkshire's second-largest stock investment, Bank of America, is less than one-fourth the size of its Apple stake.

How Berkshire's Apple stake grew

Berkshire Hathaway first reported Apple stock in its portfolio in the first quarter of 2016. It started as a small investment (for Berkshire), with the company initially spending about $1.1 billion on Apple shares at that time. It was also confirmed that Buffett didn't initiate the investment -- one of his investment managers (Ted Weschler or Todd Combs) initially pulled the trigger on it.

However, Buffett certainly had a lot to do with the current Apple investment. Over the following three-year period, Berkshire accumulated nearly 1 billion shares of Apple. It has since sold a bit, as you can see in the current share count, but there was a period when Buffett was on quite a buying spree.

A big winner for the Oracle of Omaha

In all, Berkshire paid a split-adjusted price of $39.62 per share for its Apple stake, which corresponds to an overall cost basis of about $35.9 billion. As mentioned, the investment is now worth $156 billion, which is an overall gain of over $120 billion. In terms of a percentage, this means Warren Buffett and Berkshire Hathaway are up by about 335% on their Apple investment, making it one of the biggest winners (and the biggest winner in terms of dollars gained) in the legendary investor's career.