Sierra develops agentic AI software that powers customer-facing agents handling interactions like mortgage refinancing, insurance claims, returns, and fundraising. The company reports that agents on its platform are processing billions of interactions and that more than 40% of the Fortune 50 are customers. Sierra disclosed rapid revenue growth, hitting $100 million in ARR in late November and $150 million in ARR by early February. In April the company launched Ghostwriter, an “agent as a service” tool that generates and deploys specialized agents from natural-language descriptions. Leadership includes Bret Taylor, who serves as CEO and is also chairman of OpenAI and a former co-CEO of Salesforce. After the latest raise Sierra’s valuation sits above $15 billion and it plans to use the fresh capital to scale its platform and expand product capabilities.

Total raised

$1.6B

Funding rounds

6

Latest round

Series E

Latest activity

May 2026