Sierra raises $950M Series E at $15.8B valuation

Sierra, the AI startup co-founded by Bret Taylor and Clay Bavor, has raised $950 million in a Series E round led by Tiger Global and Google’s GV. The company’s post-money valuation is $15.8 billion, up from $10 billion in September 2025.

The round also included participation from Benchmark, Sequoia, and Greenoaks, according to multiple reports. Sierra said the new capital gives it more than $1 billion to work with as it expands its AI-powered customer service products for enterprise customers.

Sierra builds AI customer service agents for businesses, positioning itself in the fast-growing market for enterprise AI agents. The company has been moving quickly on both funding and valuation, with this raise coming only months after its previous large financing round.