Ackman's Microsoft Bet: A 15% Stake and a $200 Billion OpenAI Risk

Billionaire investor Bill Ackman has significant stakes in Microsoft through his investment firm Pershing Square Capital Management. The company's portfolio allocates around 15% to a $2.4 billion stake in Microsoft, which Ackman believes will benefit from its AI strategy and capital spending over the next decade.

Ackman began buying Microsoft shares in February 2026 after the stock experienced a decline following its fiscal second-quarter report. At that time, he acquired the shares at around 21 times forward earnings, roughly in line with the broader market and below Microsoft's usual premium multiple.

Microsoft's valuation doesn't fully reflect its 27% stake in OpenAI, which Ackman estimates could be worth about $200 billion or 7% of Microsoft's market cap if it were valued independently. This is a key aspect of his thesis that the market underprices Microsoft's AI assets and overreacts to near-term spending.

Investors should be cautious not to treat Ackman's enthusiasm as a 'buy no matter what' endorsement, however. The company's massive capital spending commitments pose risks if AI demand or pricing falls short of expectations. Additionally, intense competition in AI infrastructure and concentration risk may also affect the stock's performance.