This earnings season, Big Tech didn't just make money by selling cloud services, software and advertising. It also made billions because some of the company holdings sitting in its investment portfolio — such as Anthropic and Space Exploration Technologies Corp. SpaceX (SPCX) — became significantly more valuable.

That marks an important shift for investors. Alongside businesses like Google Search, AWS and Microsoft Azure, private AI investments are beginning to play a meaningful role in the earnings of some of the world's largest public companies.

How Private Investments Show Up in Earnings

The gains aren't the result of companies selling their stakes.

Instead, accounting rules require certain equity investments to be updated to reflect their estimated market value each reporting period. When those valuations rise, companies can record an accounting gain in their income statement even if they haven't sold a single share.

In other words, soaring valuations at private AI companies can boost reported profits alongside the earnings generated by a company's core business.

That dynamic was on full display this quarter.

Billions of Dollars From Anthropic and SpaceX

Alphabet Inc. (GOOGL) (GOOG), Amazon.com Inc. (AMZN) and Microsoft Corp. (MSFT) collectively reported more than $150 billion in investment gains this earnings season, much of it tied to private AI holdings, according to company filings and media reports.

Alphabet reported roughly $98 billion in other income during the second quarter, helping drive a nearly 300% increase in earnings per share. While the company did not identify individual investments, analysts and media reports attributed much of the gain to the higher valuations of Anthropic and SpaceX.

Amazon recorded $53.4 billion in pre-tax other income, primarily from the revaluation of its investment in Anthropic, helping lift earnings per share by 242%.

Microsoft also benefited, recognizing a $3.2 billion gain from its Anthropic investment, although the company said that was partly offset by a decline in the value of its OpenAI stake.

A New Driver of the AI Boom

For years, investors measured the AI boom through chip sales, cloud revenue and software adoption.

Now there's another way AI is showing up in earnings: the rising value of the companies developing the technology.

Reuters noted that these investment gains became a meaningful contributor to the S&P 500's strong earnings growth this quarter, underscoring how intertwined public technology companies have become with the private AI ecosystem. It also means companies can benefit from the AI boom in more ways than one—not only by building and selling AI products, but also through the appreciation of strategic investments made years earlier.

Why Investors Should Watch

None of this takes away from the strength of Big Tech's core businesses. Alphabet continued to deliver strong cloud growth, Amazon posted its fastest AWS expansion in more than four years, and Microsoft maintained robust demand for its AI offerings. Those businesses remain the primary drivers of long-term value.

But this earnings season highlighted a new variable investors may need to watch.

If AI companies such as Anthropic and SpaceX continue rising in value, they could remain a meaningful tailwind for reported earnings. If those valuations level off—or decline—the opposite could also be true.

For investors, the AI story is no longer just about chips, cloud computing and chatbots. It's increasingly about the value of these companies that Big Tech already owns.