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

Larger sums, fewer total transactions. That succinctly characterizes the state of U.S. Series B startup funding in 2026, as venture capital investments remain heavily concentrated on a select group of artificial intelligence standouts.

Data from Crunchbase reveals that investors have injected roughly $48 billion into Series B stage financings so far this year 1, marking the highest aggregate total in years. Nevertheless, the total count of rounds sits below figures from a year ago and is tracking toward a multiyear low.

Smaller Series B rounds grow scarcer

A sharp drop-off in small and mid-sized Series B rounds is a primary driver behind this capital concentration.

To date this year, less than one-third of the transactions in our sample set 2 fell below the $30 million threshold. Conversely, Crunchbase figures show that transactions in this bracket comprised about half of all deals between 2021 and 2025.

The smallest Series B agreements have become especially rare, with only 26 rounds under $10 million recorded in our sample set this year.

Big rounds still a big thing

Conversely, exceptionally large Series B rounds are thriving.

At least 110 enterprises have secured $100 million or greater in funding around this stage over the course of the year, accounting for approximately one-quarter of all deals.

The largest by a wide margin among these was a $12 billion round 3 secured by Prometheus, the physical AI startup launched last year by Jeff Bezos.

Model developer World Labs, spearheaded by AI luminary Fei-Fei Li, tied for the second-largest fundraising effort by securing $1 billion in February. Additionally, nuclear energy startup Valar Atomics captured $1 billion in Series B financing across multiple tranches this year, with Sequoia Capital acting as the lead investor.

For a broader perspective, we have assembled a sample list below highlighting more of the largest U.S. Series B beneficiaries this year.

Mostly an AI story

Unsurprisingly, one of the most prominent takeaways from examining Series B recipients is that the group is overwhelmingly dominated by AI ventures.

Crunchbase data indicates that approximately two-thirds of Series B capital has gone to AI-focused startups so far this year, compared to roughly half of investments directed toward AI categories in 2025.

AI enterprises also commanded a major share of total transactions, making up over half of all reported U.S. Series B deals so far in 2026.

Bullish climate for Series B

Taken together, the figures indicate an optimistic environment for Series B investments, specifically for AI startups displaying proven traction. The market looks particularly advantageous for companies that have previously secured substantial capital during their seed and Series A phases.

Even so, the climate remains challenging for startups seeking smaller Series B rounds. Within the current AI-centric cycle, investors increasingly prefer issuing massive checks to high-valuation companies.

?Frequently Asked Questions

01What is the overall trend for U.S. Series B funding in 2026?

Total funding amounts have climbed to approximately $48 billion, but the actual number of completed deals is declining and tracking toward a multiyear low.

02How much of the Series B funding is going to AI startups?

About two-thirds of all Series B funding this year has been directed toward AI-focused companies, representing over half of all reported U.S. Series B deals.

03Are small Series B rounds still common?

No. Small and mid-sized rounds have grown scarce, with less than a third of deals falling under $30 million this year, compared to about half between 2021 and 2025.