Sierra, the San Francisco company that builds AI agents for customer service, said on May 4, 2026 that it had raised $950m from new and existing investors at a valuation of more than $15bn.
Tiger Global and GV led the round. According to CNBC, as reported by TechStartups, the post-money valuation was $15.8bn and Benchmark, Sequoia and Greenoaks also took part. Some outlets described the financing as a Series E; Sierra's announcement did not name a series.
Co-founders Bret Taylor and Clay Bavor wrote that the company now had more than $1bn to invest in becoming the standard platform for businesses moving their customer experience to AI.
“We have never had such conviction in the opportunity for Sierra and our customers.”Bret Taylor and Clay Bavor, Co-Founders, Sierra
What Sierra does
Sierra sells AI agents that handle customer conversations, including phone calls, on behalf of large companies, with customers in insurance, home lending, banking, healthcare, telecoms and retail. The company says it works with more than 40% of the Fortune 50 and that its agents handle billions of customer interactions.
In its announcement Sierra cited Nordstrom, which launched a voice agent called Nora in five weeks; Singtel, which went live in 10 weeks and reports resolution rates above 70%; and Cigna, which reached production in eight weeks and cut the time needed to authenticate patients by 80%.
TechStartups reported that Sierra passed $150m in annual recurring revenue within eight quarters and that its products run on foundation models from OpenAI and Anthropic with its own fine-tuned systems on top. Taylor told CNBC that companies spend roughly $400bn a year on customer service.
The funding so far
The round comes eight months after Sierra raised $350m at a $10bn valuation in September 2025, a round led by Greenoaks. TechCrunch reported at the time that the company had raised $635m in total, including $110m led by Sequoia and Benchmark in February 2024 and $175m led by Greenoaks in October 2024. TechStartups reported that the October 2024 round valued Sierra at $4.5bn.
Taylor, who previously held leadership roles at Salesforce, Facebook and OpenAI and chaired Twitter, and Bavor, a longtime Google executive who oversaw its virtual reality work and Google Labs, started the company in early 2024, according to TechCrunch.
Sierra did not disclose its headcount. TechStartups reported that Taylor said an IPO was in the company's future but that it planned to stay private for now.
A crowded market for AI agents
Taylor acknowledged heavy competition in AI customer service, telling CNBC that when a market draws this much excitement it ends up with too much capital and too many companies, and that Sierra was several times larger than its nearest rival.
Peter Fenton of Benchmark, an early investor, described Sierra as the leader in the customer experience category.
Fenton also argued that taking a wait-and-see approach to AI was a path to extinction for companies. Sierra's announcement listed products including Ghostwriter, Agent Studio and an Insights tool, and said the company had started with four design partners a couple of years ago.
Company website: sierra.ai