In his annual letter to shareholders, the 93-year-old investing legend reassured investors that Berkshire was 'built to last', but toned down expectations, saying it did not have many lucrative investment opportunities left.

He said Berkshire would perform slightly better than the "average American corporation," but anything beyond that is "wishful thinking," even as it had a cash pile of $167.6 billion.

Berkshire's Class B stock, which carry higher voting rights and whose value was 1/1,500th of Class A shares, was trading at $435.50. Investors closely watch Berkshire as its results are often seen as a bellwether for the U.S. economy.

"There remain only a handful of companies in this country capable of truly moving the needle at Berkshire, and they have been endlessly picked over by us and by others... All in all, we have no possibility of eye-popping performance," Buffett wrote.

He also mourned the passing of his longtime second-in-command Charlie Munger in his annual letter, while assuring investors that vice Chairman and designated successor Greg Abel was "ready to be CEO of Berkshire tomorrow."

Berkshire's annual operating profit climbed 21% to $37.4 billion on improved underwriting and higher investment income from the insurance segment. Operating profit for the fourth quarter also came in ahead of analysts' expectations.