Sierra raised $950 million in a Series E funding round.
Former Salesforce co-CEO Bret Taylor founded the artificial intelligence startup.
Tiger Global and GV, formerly Google Ventures, co-led the investment.
The round gives the company a post-money valuation of $15.8 billion.
This valuation marks an increase from the $10 billion level reached in 2025.
Sierra develops AI-powered conversational agents for enterprise customer service.
The technology automates and improves how businesses interact with customers.