Series B Funding Is Up, But Fewer Deals Are Getting Done

More money, fewer rounds. That, in short, is the state of U.S. Series B startup funding in 2026, as venture capital investment continues to concentrate heavily around a handful of AI hotshots.

Crunchbase data shows that so far this year, investors have poured around $48 billion into financings around the Series B stage 1, the highest tally in years. Yet round counts are below year-ago levels and are on track for a multiyear low.

Smaller Series B rounds grow scarcer

One trend driving capital concentration is a sharp decline in small and mid-sized Series B rounds.

So far this year, less than a third of deals in our sample set 2 were for under $30 million. By contrast, between 2021 and 2025, rounds in this range accounted for about half of deals, per Crunchbase data.

The smallest Series B deals have gotten particularly scarce. This year there were just 26 rounds under $10 million in our sample set.

Big rounds still a big thing

On the flip side, really large Series B rounds are quite popular.

At least 110 companies have raised rounds of $100 million or more around this stage so far this year. That’s roughly a quarter of all deals.

Of these, the largest by far was a $12 billion round 3 for Prometheus, Jeff Bezos’ physical AI startup that launched last year.

Model developer World Labs, led by AI pioneer Fei-Fei Li, was tied for next-biggest fundraiser, closing on $1 billion in February. Nuclear energy startup Valar Atomics also secured $1 billion in Series B funding across tranches this year, with Sequoia Capital as lead investor.

For a wider snapshot, below we put together a sample list of more of this year’s biggest U.S. Series B recipients.

Mostly an AI story

Meanwhile, one of the least surprising findings from our analysis of Series B recipients is that it was a heavily AI-focused group.

So far this year, about two-thirds of Series B funding has gone to AI-focused startups, per Crunchbase data. In 2025, by comparison, about half of investment went to companies in AI categories.

AI companies were also heavily represented by round count. So far in 2026, more than half of all reported U.S. Series B deals have been for AI companies.

Bullish climate for Series B

Overall, the numbers point to a bullish climate for Series B investment, particularly for AI startups with demonstrated traction. The environment looks particularly favorable for companies that have already raised considerable sums at Series A and seed.

Even so, these don’t look like the best of times for startups seeking smaller Series B rounds. Seems like in the current AI-driven cycle, investors are increasingly focused on big checks for high-valuation companies.

Related Crunchbase query:

Illustration: Dom Guzman

May include rounds that have characteristics of Series B financings but were not explicitly announced as Series B deals.↩

Sample included U.S. Series B rounds of $1 million or more.↩

Prometheus did not publicly announce its $12 billion funding round as a Series B, but reports from multiple sources, including an Axios post, described it as Series B.↩

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Source: Crunchbase News