Amazon's Stake in Anthropic Could Be Worth Over $400 Billion If the AI Start-Up's Reported IPO Valuation Holds. Should Jeff Bezos' Amazon Investors Care?

One of the most impressive investments at the corporate level in recent years has been Amazon's (NASDAQ: AMZN) decision to take an early stake in Anthropic. The tech giant invested $8 billion in the artificial intelligence start-up in 2024, then followed that up with an additional $5 billion investment this year.

Combined, those moves gave Amazon a reported 21% stake in Anthropic, the developer of the Claude chatbot and family of large language models. And they have paid off in a big way. According to Amazon's quarterly financial reports, its Anthropic stake was valued at $190.4 billion as of the end of June, including $97.9 billion in convertible notes and $92.5 billion in nonvoting preferred stock.

But that calculation was based on a May 2026 funding round that valued Anthropic at $965 billion, and it's already being valued at much more than that. In early July, secondary markets were valuing Anthropic at $1.2 trillion in anticipation of the company going public as early as October.That would bring Amazon's stake to a whopping $252 billion.

And more recent estimates from secondary markets put Anthropic's valuation at much higher -- $2 trillion or more. If Anthropic is successful in that offering (it submitted its confidential S-1 form to the Securities and Exchange Commission earlier this year to explore the possibility), Amazon's stake in it would be valued at roughly $420 billion.

Amazon executive chairman Jeff Bezos. Image source: Amazon.

The bigger Anthropic gets, the better it is for Amazon

Amazon could book a huge profit from its Anthropic shares, should it ever want to divest itself of some of them. But considering how fast Anthropic is growing, it may be hard for Executive Chairman Jeff Bezos and CEO Andy Jassy to pull the trigger on a sale.

Let's look at how the Anthropic stake has become an increasingly larger part of Amazon. By doing so, we'll look at four data points.

Data sources: Amazon filings, Macrotrends. *Targeted IPO valuation. **Amazon's market cap as of Aug. 17, 2026.

For this example, we'll look at the value of Amazon's stake in Anthropic as reported by the company in its two most recent quarterly filings and compare it to the company's market cap. At the end of March, Anthropic accounted for only 3.4% of Amazon's value, but that share climbed to 7.4% by the end of June as Anthropic's valuation rose.

If Anthropic achieved a $1.2 trillion valuation in its IPO -- a conservative estimate, given how secondary markets are pricing the start-up now -- its Anthropic shares would be nearly 9% of Amazon's value. But based on a $2 trillion valuation -- assuming that Amazon's market cap stays roughly at its current level for the next two months or so -- that Anthropic stake is providing nearly 15% of Amazon's value.

With all this in mind, Amazon investors should be watching the Anthropic news closely. The bigger the AI startup gets, the more important it is to Amazon. Based on its current outlook, Bezos and Jassy could realize a windfall if they sell some or all of those shares -- money that could help fund Amazon's aggressive AI build-out. And if Anthropic's valuation craters, Amazon would be looking at big paper declines.

Either way, though, Amazon's $13 billion investment has been amazingly profitable -- and it may just be in the opening stages.

Patrick Sanders has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Amazon. The Motley Fool has a disclosure policy.