Sierra Raises $950M Series E at $15.8B Valuation as Enterprise AI Agent Demand Surges

Sierra, the enterprise AI agent platform co-founded by OpenAI chairman Bret Taylor and former Google executive Clay Bavor, raised $950 million in a Series E round led by Tiger Global and Google's GV, with participation from Benchmark, Sequoia, and Greenoaks. The round values the company at $15.8 billion post-money, up from $10 billion in fall 2025 and $4.5 billion in October 2024. Sierra reports $150 million in annual recurring revenue as of early February, up from $100 million in late November, and claims over 40% of the Fortune 50 as customers. The company's agents handle billions of interactions across mortgage refinancing, insurance claims, and customer service. Sierra recently launched Ghostwriter, a tool that autonomously builds and deploys specialized AI agents from natural language descriptions. The raise gives Sierra over $1 billion in total capital and signals intense investor competition to back category winners in enterprise agentic AI.