Bill Ackman Amazon Investment: Why the Hedge Fund Legend Keeps Betting Big on Andy Jassy’s Empire

As recently as the spring of 2025, Bill Ackman had no shares in Amazon. Given that the position has grown to be the largest holding in his $19.5 billion Pershing Square portfolio—currently valued at about $2.9 billion and accounting for nearly 20% of the fund’s reported assets—it is important to keep that in mind. That kind of allocation in a little more than a year is a warning sign for a manager known for concentrated, high-conviction bets.

After purchasing shares the month before, Ackman initially revealed the Amazon stake in May 2025. AWS, Amazon’s cloud computing division, had just reported a 17% increase in revenue over the previous year. Strong, but not particularly impressive in terms of technology. Ackman reportedly noticed the direction of travel in addition to the number itself. The argument is simple, as Pershing Square has since reaffirmed to investors: AI infrastructure demand and e-commerce’s ongoing strength will propel Amazon’s earnings growth at a rate of more than 20% annually. Thus far, the execution has closely matched that expectation.

Pershing Square added about 3.78 million shares in Q4 alone, increasing its stake in Amazon by 65% by the end of 2025. In Q1 2026, there was an additional 19% increase. Even as Ackman was selling out of Alphabet completely, the position continued to grow. In a May 2026 post, he explained that he had freed up the money specifically to fund Microsoft exposure. Microsoft in, Alphabet out. Amazon remains. You can infer something about his current perception of the risk-reward balance from that sequencing.

It’s noteworthy that the larger hedge fund community seems to concur. In recent quarters, Seth Klarman’s Baupost Group, Al Gore’s Generation Investment Management, and David Tepper’s Appaloosa Management have all increased their Amazon stakes. It has grown to be Tepper and Klarman’s single largest holding. It’s rarely a coincidence when so many respected value investors choose the same name at about the same time. When the majority of these positions were being assembled, the stock had only increased by roughly 10% over the previous year, and they are all looking at the same gap: a rapidly expanding company.

It takes some time to comprehend the valuation argument. Compared to Microsoft or Nvidia, which trade at 18 to 20 times forward earnings, Amazon appears pricey at about 27 times. It is more expensive than the Nasdaq 100 on paper. However, a massive capital expenditure cycle is compressing that multiple. According to Amazon, it plans to spend about $200 billion on infrastructure in 2026, primarily for AWS. The stock appears more expensive than the underlying business performance may indicate because of this expenditure’s significant impact on short-term earnings.

According to the sum-of-the-parts argument, AWS alone is worth nearly half of the company’s total market capitalization, growing at a rate of 28% annually and having a contracted backlog of $364 billion. Retail, advertising, streaming, and a ten-year agreement with Anthropic to spend more than $100 billion on AWS are all included at a price that is more akin to a discount.

However, it’s difficult to ignore the significant change that occurred in Q2 2026. Selling about 2.9 million shares, Pershing Square reduced its Amazon stake by about 25% while joining Microsoft. That is a recalibration rather than a reversal of the thesis. Amazon’s stock increased by about 10% since the end of the second quarter, while Microsoft’s stock increased by about 30% during the same period due to impressive earnings. It’s unclear from the 13F filings alone whether Ackman is managing concentration risk or rotating capital toward better near-term momentum.

The fact that Amazon’s business has continued to deliver is evident. During Ackman’s tenure, AWS’s growth increased from 17% to 28%. The Anthropic partnership, cloud backlog, and operating income all show the same trend. The thesis is still intact. It’s possible that the trimming has less to do with uncertainty and more to do with discipline, which Ackman has always excelled at.