Series B funding in the U.S. reached $48 billion so far in 2026, the highest in years, yet deal counts fell below year-ago levels and track toward a multiyear low, according to Crunchbase data. The concentration reflects a sharp decline in smaller rounds. Less than a third of Series B deals this year were under $30 million, compared to about half between 2021 and 2025. Only 26 rounds under $10 million closed in the sample set so far in 2026.
Large rounds dominate the landscape. At least 110 companies raised $100 million or more at the Series B stage, roughly a quarter of all deals. Prometheus, Jeff Bezos' physical AI startup, secured the largest round at $12 billion. World Labs, led by AI pioneer Fei-Fei Li, closed a $1 billion Series B in February. Nuclear energy startup Valar Atomics also raised $1 billion in Series B funding across tranches, with Sequoia Capital as lead investor.
AI companies captured roughly two-thirds of Series B funding so far in 2026, up from about half in 2025. More than half of all reported U.S. Series B deals went to AI-focused companies.
The funding environment favors Series B companies with demonstrated traction and prior capital raises at Series A and seed stages. Startups seeking smaller Series B rounds face a tougher climate.