Jeremy Grantham delivered sharp warnings on CNBC’s Squawk Box. The GMO co-founder called cryptocurrency a useless speculative mechanism destined to fade. Markets sit at their most expensive levels in American history, he said.
Grantham appeared on June 26, 2026. He spoke plainly about Bitcoin, broader crypto assets, and stretched valuations that have persisted for years. His comments echoed long-held views but landed amid fresh market highs and ongoing AI enthusiasm.
Grantham dismisses crypto while praising blockchain tech.
Crypto lacks any stable form of value, Grantham argued. It rose for no particular reason in a strong economy. He predicted it would dwindle away, not with a bang but a whimper. Proof of unnecessary work should not be worth a bucket of warm spit, he added.
Bitcoin draws comparison to arbitrary historical mediums like shells on an island. Faith drives its price. Grantham separated blockchain technology, which he called real and potentially transformative, from the speculative frenzy around tokens. Crypto’s main practical use remains enabling anonymous transactions for those seeking to move money without a trace.
He contrasted crypto unfavorably with gold. Gold has delivered strong long-term gains despite volatility and serves practical purposes in serious trades. Crypto offers none of that reliability. Grantham aligned with critics like Warren Buffett and Charlie Munger. He suggested crypto may not survive a significant bear market of 50 to 70 percent declines. The current bull market has run since March 2009.
CNBC covered the appearance in segments titled Billionaire investor Jeremy Grantham on crypto: A useless, speculative mechanism and Billionaire investor Jeremy Grantham: This is the most expensive market in American history. X posts from the day echoed his remarks, with traders noting the blunt language on Bitcoin going to zero eventually.
Grantham has considered the market overpriced by long-term standards since the S&P 500 hovered around 2,300 in April 2021. He referenced his history of calling bubbles, including the Japanese asset bubble, the dot-com era, and excesses before the 2008 financial crisis. When pressed on his bearish stance amid years of gains, he pointed to GMO quarterly letters and performance at a family foundation. The foundation outperformed major endowments like Harvard and Yale on a 10-year basis until roughly five years ago, when green tech investments faced headwinds from political and regulatory shifts.
AI enthusiasm fits classic bubble patterns, he warns.
Grantham views major technological innovations as classic bubble drivers. Railroads, the internet, and now AI follow the same script. The current environment features one of the biggest investment bubbles in American history, fueled by AI enthusiasm. Geopolitical tensions, trade issues, and other risks form a dangerous backdrop.
Signs of frothiness appear everywhere. Grantham highlighted euphoria around names like SpaceX, whose addressable market claims reach a quarter of global GDP. Mining asteroids and AI success stories sound like classic descriptions of a market peak. He discussed a potential SpaceX IPO and broader economic signals in the interview.
Bloomberg reported similar themes in a June 18, 2026 Odd Lots episode. Grantham recounted spotting the dot-com bubble and drew parallels to today’s AI excitement in his memoir The Making of a Permabear: The Perils of Long-Term Investing in a Short-Term World. GMO’s January 2026 research note Valuing AI: Extreme Bubble, New Golden Era, or Both argued the boom meets every condition of prior innovation bubbles. Big Tech capex alone reached nearly $300 billion in 2025 from Amazon, Alphabet, Meta, and Microsoft.
Grantham built his reputation correctly identifying those earlier excesses. Critics label him a permabear. He frames the approach as disciplined long-term investing in a world obsessed with short-term gains. Mean reversion remains central to his philosophy. Short-term thinking carries clear perils.
His core message stayed consistent. Speculative fervor around assets like crypto and parts of the AI trade detaches from fundamental value. Investors should remain cautious amid elevated valuations. Focus on mean-reverting assets and quality businesses at reasonable prices, often found more readily outside the U.S. or in less-hyped sectors. Maintain a long-term perspective rather than chasing momentum.
The full Squawk Box interview clips sit on the CNBC YouTube channel. Grantham’s views represent one experienced perspective. Investors conduct their own due diligence. Markets can remain irrational longer than expected. History shows extremes in valuation and speculation eventually correct.
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