Bill Ackman has been quietly buying Microsoft since February, when AI fears were dragging the stock

Pershing Square Capital Management, the hedge fund run by the billionaire investor, has built a new position in the software giant. 

And in typical Ackman fashion, he disclosed the stake in his trademark style: a lengthy post on X on Friday ahead of his firm’s quarterly 13F filing (a required filing for institutional investment managers with over $100 million in assets). He did not disclose the size, but called it a “core holding.”

Pershing started accumulating shares in February, after Microsoft’s stock fell about 10% the day after Q2 earnings, with a 1% lower-than-expected cloud growth alongside a surge in capital spending. “We were able to establish our position at a valuation of 21 times forward earnings, broadly in line with the market multiple and well below Microsoft’s trading average over the last few years,” Ackman wrote in the post.

Microsoft’s stock is down more than 15% year-to-date as it fights to prove that its Azure cloud business has enough revenue to justify its AI spending. The erosion of its partnership with AI, which was recently restructured to strip Microsoft of exclusive distribution rights, only furthered those concerns.

Ackman sees that restructuring as a pivot to a multi-model architecture that can better suit the needs of its enterprise customers.

He also argues that investors underestimate Microsoft’s 365 productivity suite and its stickiness, saying the suite is “deeply embedded” in enterprises and “nearly impossible to replicate,” he wrote.

Ackman pushed back on concerns over Microsoft’s $190 billion 2026 capex budget, arguing it as growth investment on a J curve rather than a threat to margins. He also pointed out that Microsoft’s market capitalization does not yet reflect its 27% economic interest in OpenAI— worth approximately $200 billion at the startup’s most recent funding round valuation, he said.

The Microsoft buy continues Ackman’s pattern of stepping into Big Tech during periods of AI-related skepticism.

“We acquired Alphabet when the stock declined substantially on the release of ChatGPT in late 2022, Amazon in the weeks following Liberation Day, and Meta more recently on the market’s response to the company’s unexpectedly large capex guidance,” he wrote.