U.S. Series B Funding Swells to $48 B in 2026 While Deal Count Hits Multi-Year Low

Investors have poured roughly $48 billion into U.S. Series B rounds so far in 2026, the highest total recorded in recent years, even as the number of deals falls below last-year levels and heads toward a multi-year trough. The disparity reflects a pronounced shift toward a handful of large, AI-focused financings and a retreat from modest-sized rounds.

Data from Crunchbase show that under one-third of the Series B deals in the current sample are for amounts below $30 million. By contrast, between 2021 and 2025, roughly half of all Series B rounds fell into that bracket. The scarcity is most acute at the low end: only 26 rounds under $10 million have been recorded this year. Meanwhile, at least 110 companies have secured Series B checks of $100 million or more, representing about a quarter of all reported deals.

The most striking example is a reported $12 billion Series B raise by Prometheus, Jeff Bezos’s physical-AI startup that launched last year. The next-largest financings were $1 billion rounds by World Labs, led by AI pioneer Fei-Fei Li, and by nuclear-energy venture Valar Atomics, which closed its $1 billion Series B across multiple tranches with Sequoia Capital as lead investor. These mega-checks underscore a market that rewards companies with substantial traction and high valuations.

AI-centric firms dominate the funding landscape. Approximately two-thirds of the $48 billion in Series B capital has flowed to AI-focused startups, up from about half of the allocation in 2025. More than half of all reported U.S. Series B deals this year involve AI companies, indicating that venture capital is concentrating on the sector’s perceived growth potential.

The environment appears especially favorable for startups that have already amassed sizable seed and Series A rounds. Companies with proven product-market fit and sizable early-stage backing are attracting the bulk of the capital, while founders seeking smaller, incremental Series B checks face a tightening market. The trend suggests investors are prioritizing large, high-valuation opportunities that can deliver outsized returns in an AI-driven cycle.

Looking ahead, the concentration of capital in a limited set of AI megadeals could shape the competitive dynamics of the broader startup ecosystem. Founders of non-AI or smaller-scale ventures may need to explore alternative financing routes or demonstrate differentiated traction to capture investor interest. As the venture community continues to allocate disproportionate resources to a few high-profile AI players, the question remains whether the current funding pattern will sustain long-term innovation across the wider tech landscape.