Eight Sleep, the New York-based “sleep fitness” company, announced a $50 million Series D led by Tether Investments. The round values the startup at $1.5 billion, building on a cumulative capital base of more than $310 million.
The cash infusion will fund the rollout of new AI-driven product lines, deeper international expansion, and the pursuit of FDA clearance for medical-grade sleep apnea solutions. Eight Sleep already ships its smart mattress accessories to over 34 countries and turned cash-flow positive in 2025.
Capital Fuels Global Footprint
Eight Sleep will deploy a portion of the capital to broaden its presence in key markets such as China, Singapore, and additional European territories. The company already serves customers in more than 30 countries and plans to open its own retail showrooms where consumers can experience the Pod in-person. “We find in our marketing/purchasing journey that people would like to try the product,” said co-founder and VP of Brand & Marketing, Alexandra Zatarain.
AI Sleep Agent Changes Lives and Habits
The round accelerates development of the company’s Sleep Agent, a large-language-model-backed system that creates thousands of digital twins per user to simulate temperature, elevation, and firmness adjustments before bedtime. Early pilots have already prompted users to shift exercise timing, caffeine intake, and sleep schedules based on AI-generated insights. “What we’re building doesn’t exist yet, a system that understands your body better each night and acts on that knowledge,” said CEO Matteo Franceschetti.
Medical-Grade Expansion and FDA Pathway
Eight Sleep is leveraging its clinical-grade sensors to launch condition-specific interventions, starting with menopausal hot-flash relief and contactless sleep-apnea detection. The company is actively pursuing FDA approval to position the Pod as a prescribable treatment, aiming to move the product from consumer wellness into reimbursable medical care. “We’re not replacing your doctor, but we are giving you nightly, high-accuracy health monitoring so you can act early if trends shift,” added Zatarain.
Revenue Engine and Profitability
Since the Pod’s 2019 debut, Eight Sleep has generated more than $500 million in sales and achieved being free-cash-flow positive in 2025. The lean operation, with just over 100 full-time employees, has scaled revenue tenfold since 2020 while maintaining a subscription model that underpins recurring revenue streams. Existing investors such as HSG, Valor Equity Partners, Founders Fund, and Y Combinator continue to back the company, reinforcing confidence in its growth trajectory.
Why Zillionize Invested
Zillionize, a prominent seed round investor, has been championing technological startups since March 2011. We see Eight Sleep as the rare convergence of hardware, data, and AI that is redefining sleep from a passive experience to an active health platform. Eight Sleep’s tactical leadership, proven revenue growth, cash-flow position, and clear roadmap toward regulated medical applications align with our focus on deep-tech ventures that can capture both consumer and enterprise value. Our portfolio boasts investments in several unicorns, and we’re delighted to have Eight Sleep on that list.