California has long been a magnet for bold ideas and daring entrepreneurs. In 2025, the state’s startup ecosystem once again proved its strength with a wave of Series B funding rounds that propelled emerging tech companies into the next stage of growth.
Series B is the point where an idea transforms into a scalable operation, where leadership teams sharpen their market position, and where investors signal confidence in a company’s ability to dominate its sector.
This post highlights ten California-based startups in the technology space that secured Series B funding in 2025. The companies are listed from the smallest to the largest funding amount, giving you a clear view of how investment levels vary across the spectrum. For each one, we look at what they do and who is betting on their success.
Novoloop – $21M
Novoloop, based in Menlo Park, is making waves in the climate tech sector by turning low-value waste plastics into high-performance thermoplastic polyurethane (TPU).
Their proprietary process chemically upcycles polyethylene waste, which is often destined for landfills or incineration, into materials that can be used in products like sneakers and automotive parts. This approach addresses two critical challenges: reducing plastic waste and lowering the carbon footprint of manufacturing.
Founded by Miranda Wang and Jeanny Yao in 2015, the company evolved from its early incarnation as BioCellection into a leader in chemical recycling.
The Series B funding round, worth $21 million and led by Taranis with participation from Valo Ventures and Shop Limited, will be used to design and build their first commercial-scale facility. That leap will test Novoloop’s ability to deliver on its promise at an industrial scale.
The company’s success could set a precedent for sustainable materials innovation, positioning it as both an environmental champion and a supplier of valuable raw materials for high-demand industries. The broader implication is a more circular economy, where waste becomes a resource rather than a burden.
Arbital Health – $31M
San Francisco’s Arbital Health operates in the complex world of value-based care, where healthcare providers and insurers share financial risk tied to patient outcomes.
Their AI-powered platform simplifies the process by centralizing and reconciling data from both sides, automating calculations, and offering real-time performance tracking. This kind of infrastructure is essential for making outcome-based care practical and scalable.
Founded in 2024 by Brian Overstreet and Travis May, Arbital brings together deep experience in healthcare technology and data infrastructure. The $31 million Series B round was led by Valtruis, with support from Transformation Capital, Shaper Capital, and Healthy Ventures.
The funds will expand their engineering and actuarial teams, enabling them to handle a growing number of healthcare organizations.
With over 600,000 patient lives already managed on the platform, Arbital’s growth trajectory suggests that better data and transparency could transform how healthcare rewards are distributed, ultimately benefiting both providers and patients.
Sparrow – $35M
Sparrow is transforming the often-overlooked process of employee leave management. The San Francisco-based company offers an end-to-end platform that automates workflows, ensures compliance, and creates a smoother experience for employees and HR teams alike.
From parental leave to medical absences, Sparrow takes care of the heavy lifting so employers can focus on supporting their teams.
Founded in 2019 by Deborah Hanus and Samarth Keshava, Sparrow has built a strong client base that includes OpenAI, Reddit, and Chime. Their $35 million Series B round, led by SLW, brings their total funding to $64 million. This capital will help expand their product capabilities and reach new markets.
By removing administrative bottlenecks and reducing compliance risks, Sparrow positions itself as a crucial partner for companies navigating increasingly complex employment laws and workplace expectations.
Sprinter Health – $55M
Menlo Park’s Sprinter Health is bridging the gap between telehealth and in-person care by sending nurses directly to patients’ homes. Their on-demand healthcare service covers lab draws, preventive screenings, and other diagnostics, all coordinated through a logistics platform that ensures efficiency and convenience.
Co-founded in 2021 by Max Cohen and Cameron Behar, Sprinter Health operates in 18 states and has grown revenue sixfold in just one year.
Their $55 million Series B round, led by General Catalyst with participation from Andreessen Horowitz and other investors, brings their total funding to $125 million. The company plans to use the funds to expand its clinical workforce and operations.
By making healthcare more accessible without sacrificing quality, Sprinter Health could reshape the way patients engage with preventive and routine care, potentially reducing strain on overburdened clinics and hospitals.
Rain – $75M
Rain, headquartered in Los Angeles, offers employees early access to earned wages through a simple mobile app. The fintech company integrates with payroll systems to allow workers to draw from their paychecks before the standard payday, while also providing tools for financial wellness.
Founded in 2019 by Alex Bradford and Jen Terrell, Rain has already facilitated more than $2 billion in early wage payouts to over 2.5 million employees. The $75 million Series B round, led by Prosus with participation from Nextalia Ventures, Spark Growth, QED, and Invus, values the company at $340 million.
This model addresses a growing demand for flexible pay, offering employees more control over their finances and potentially reducing reliance on high-interest credit products. For employers, it’s a low-friction benefit that can improve recruitment and retention.
Rillet – $70M
Palo Alto-based Rillet is redefining accounting software with an AI-native ERP platform for finance teams. The system automates key workflows like accruals, reconciliations, and revenue recognition while integrating with a wide array of business tools to provide real-time financial insights.
Founded in 2021 by Nicolas Kopp and Stelios Modes, Rillet’s rapid growth is fueled by the appeal of replacing legacy systems with a modern, AI-driven solution. The $70 million Series B, co-led by Andreessen Horowitz and ICONIQ Capital, came just 12 weeks after their Series A, pushing the company’s valuation to around $500 million.
Rillet’s approach could significantly reduce the time and complexity involved in closing books, giving CFOs the agility to make faster, data-backed decisions in dynamic markets.
Harbinger – $100M
Harbinger, based in Los Angeles, focuses on medium-duty electric trucks, a segment often overlooked in the EV industry. Their modular chassis design can be adapted for delivery vehicles, RVs, and other applications, providing a versatile foundation for fleet electrification.
Founded in 2022 by John Harris, Phillip Weicker, and Will Eberts, the company draws on deep industry experience from stints at Faraday Future and Canoo. The $100 million Series B round, co-led by Capricorn Investment Group and Leitmotif Ventures, will accelerate production and commercialization.
By concentrating on one core product and leveraging proprietary manufacturing techniques, Harbinger is positioning itself as a high-quality, cost-efficient option for businesses seeking to transition to electric fleets.
Mercor – $100M
San Francisco’s Mercor is an AI-driven recruiting platform that automates sourcing, screening, and even parts of onboarding. Employers can rely on its chatbot-based interviews and resume evaluations to identify top talent more efficiently.
Founded in 2023 by Brendan Foody, Adarsh Hiremath, and Surya Midha, Mercor has grown rapidly, attracting high-profile clients like OpenAI. The $100 million Series B round, led by Felicis Ventures, values the company at $2 billion.
As competition for technical talent intensifies, Mercor’s promise to reduce bias and improve candidate matching positions it as a potential game-changer in the recruitment industry.
Harmonic – $100M
Harmonic, headquartered in Palo Alto, develops what it calls Mathematical Superintelligence—AI systems designed to solve complex problems with provable accuracy.
Their flagship model, Aristotle, focuses on generating error-free code and mathematical solutions for industries where precision is non-negotiable.
Founded in 2023 by Vlad Tenev and Tudor Achim, Harmonic secured $100 million in Series B funding led by Kleiner Perkins, with Paradigm and other notable investors participating. The funds will be used to refine Aristotle and expand its applications.
This focus on mathematical rigor differentiates Harmonic from more general AI ventures, targeting sectors like finance, aerospace, and blockchain that demand exactness.
NewLimit – $130M
San Francisco’s NewLimit is tackling one of humanity’s oldest challenges: aging. The biotech startup is working on therapies that use epigenetic programming to rejuvenate cells and extend a healthy human lifespan.
Founded in 2021 by Brian Armstrong, Blake Byers, and Dr. Jacob Kimmel, NewLimit’s $130 million Series B was led by Kleiner Perkins and drew participation from a host of prominent investors, including Khosla Ventures and Patrick Collison.
The company is already reporting promising lab results, with prototype drugs that restore youthful function to aged liver cells.
While human trials are still in the future, NewLimit’s work could usher in an era where age-related diseases are preventable and health spans are significantly extended.
A Year of Bold Bets and Bigger Ambitions
The ten companies featured here show how Series B funding can act as both a milestone and a launchpad. Each one has moved beyond proving its concept to building the infrastructure, partnerships, and teams needed for rapid growth.
From Novoloop’s push toward a circular economy to NewLimit’s pursuit of longevity breakthroughs, these ventures demonstrate the breadth of innovation emerging from California’s tech ecosystem in 2025.
This mix of sectors—climate tech, fintech, AI, healthtech, and advanced manufacturing—highlights a defining characteristic of the state’s startup culture: the willingness to tackle complex, high-impact problems with speed and creativity.
Investors have committed significant resources because they see leadership teams capable of scaling operations, entering new markets, and setting new industry standards.
The year’s funding rounds also underscore the competitive advantage of building in California, where talent density, capital availability, and a culture of risk-taking converge.
For those watching the next wave of market leaders take shape, these Series B success stories signal that the state’s role as a hub for transformative companies remains strong.
If you want to discuss how we can support your next big idea, connect with us to learn more about our software development services, and follow us on LinkedIn for more tech trends.
FAQ
What is Series B funding, and why is it important for startups?
Series B funding is a stage in a startup’s investment lifecycle where the company has already validated its product-market fit and proven its business model.
This round helps the company scale operations, expand into new markets, and build out its team. It often signals strong investor confidence in the startup’s ability to achieve significant market leadership.
How were these 10 companies selected for the list?
The companies were chosen based on publicly available funding announcements in 2025, their headquarters being in California, and their focus on technology-driven solutions. They were then ranked by the amount raised in their Series B rounds, from smallest to largest.
Which industries do these Series B companies represent?
The list covers a wide range of technology-driven sectors, including climate tech, healthtech, fintech, artificial intelligence, electric vehicles, and biotech. This diversity reflects the breadth of innovation thriving within California’s startup ecosystem.
Which company raised the largest Series B funding in 2025 on this list?
NewLimit, a biotech company aiming to extend a healthy human lifespan through cellular reprogramming, secured the largest Series B round at $130 million.
How can funding at this stage impact a startup’s growth?
Series B funding typically enables companies to accelerate product development, invest in talent acquisition, scale manufacturing or operations, and enter new geographic or vertical markets. It also helps strengthen market positioning against competitors.
How can I connect with your team for collaboration or services?
If you want to discuss how we can support your next big idea, connect with us to learn more about our software development services, and follow us on LinkedIn for more tech trends.
