Sierra Raises $950 Million At $15 Billion Valuation, 40% Of Fortune 50 Now Using Its AI Agents

Sierra Closes $950M Series E at $15.8B Valuation

Sierra (@SierraPlatform), the enterprise AI customer experience platform co-founded by @btaylor, has raised $950 million in a Series E funding round. The round was led by Tiger Global and Google's GV, with participation from Benchmark, Sequoia, Greenoaks, and others. The fresh capital values the San Francisco-based company at $15.8 billion post-money.

Sierra was founded three years ago by OpenAI Chairman and former Salesforce co-CEO Bret Taylor, alongside former Google executive Clay Bavor. The company started with just four design partners and has since grown into one of the more prominent names in enterprise AI.

With this raise, Sierra now has more than $1 billion to invest in becoming the global standard for companies wanting to transform their customer experiences with AI. Taylor estimates that $400 billion is spent annually on customer service — a bulk of which, he says, is moving to AI agents.

From Four Design Partners to 40% of the Fortune 50

Sierra claims to have more than 40% of the Fortune 50 as customers, with agents on its platform handling billions of interactions — from refinancing mortgages to processing insurance claims, managing returns, and powering nonprofit fundraising campaigns.

Named clients include WeightWatchers, SiriusXM, Sonos, ADT, Chime, Cigna, Nordstrom, Nubank, Ramp, Rivian, Rocket Mortgage, Singtel, Sutter Health, and Wayfair.

Revenue growth has been equally striking. Sierra topped $150 million in annual recurring revenue within eight quarters — a growth timeline Taylor described as unprecedented in traditional software, highlighting "intense demand in the market." The company first crossed the $100M ARR mark in late November before reaching $150M ARR by early February.

Sierra's platform focuses on conversational AI agents capable of handling complex customer service interactions without constant human oversight. Unlike chatbots that follow rigid scripts, Sierra's agents use large language models to understand context, navigate ambiguous requests, and escalate when needed.

Taylor pointed to a broader structural shift: "There's a really big addressable market and immediate opportunity. We've sort of digitized the last remaining analog channel, which is the telephone line — it's a better experience. You don't need to wait on hold. These agents are naturally multilingual."