Sierra
Conversational AI agents for customer experience; founded by OpenAI Chair Bret Taylor
SectorsAI Software
Market Metrics
Valuation (May 2026 Series D)
$15.8B
+58% from $10B (Oct 2025)
Annualized Revenue (2026)
~$200M
$150M Feb 2026; $100M Nov 2025
Customer Reach
>40% of Fortune 50
agents handle billions of interactions across CX verticals
Founder Pedigree
Bret Taylor (OpenAI Chair)
Former Salesforce co-CEO, Facebook CTO, Google Maps co-creator; current OpenAI Board Chair
Updated at 2026-Q2
Funding History
Total raised: ~$1.6B · Latest valuation: $15.8B
| Round | Date | Amount | Valuation | Key Investors |
|---|---|---|---|---|
| Seed / Series A | Feb 2024 | $110M (cumulative) | $1B | Benchmark (lead)SequoiaRavi Gupta (Benchmark)Pat Grady (Sequoia) |
| Series B | Oct 2024 | $175M | $4.5B | Greenoaks (lead)BenchmarkSequoiaThrive Capital+1 more |
| Series C | Oct 2025 | $350M | $10B | Greenoaks (lead, per The Information)SequoiaThrive CapitalICONIQ |
| Series D | May 2026 | $950M | $15.8B | Tiger Global (co-lead)GV (co-lead)BenchmarkSequoia+1 more |
Updated at 2026-Q2
Product Specifications
| Product | Type | Status |
|---|---|---|
| Sierra Agent Platform | Build + deploy + monitor conversational AI agents (chat + voice) | GA |
| AgentOS | Runtime + observability + guardrails for production agents | GA |
| Voice Agents | Phone-channel conversational AI with sub-second latency | GA (Feb 2025) |
| Sierra Benchmark / TAU 2.0 | Open-source agent-evaluation benchmark | Released |
| Agent Outcomes | Outcome-based pricing tied to resolution / containment / CSAT | GA |
Updated at 2026-Q2
Partnerships & Investors
OpenAI / Anthropic / GoogleModel Suppliers
Model-agnostic; routes per task; Bret Taylor's OpenAI board role drives no exclusivity.
SiriusXMAnchor Customer
Subscription + listener support across the SiriusXM and Pandora brands.
SonosAnchor Customer
Customer support for the troubled 2024 app launch and ongoing.
WeightWatchersAnchor Customer
Coaching + member-support agent; one of the first Sierra reference deployments.
ADTAnchor Customer
Home-security customer service; high-stakes / regulated vertical.
Discover / Brex / ChubbFinancial-Services Customers
Regulated-industry agent deployments.
Casper / OluKai / SunrunConsumer-Brand Customers
DTC and home-services reference customers.
Updated at 2026-Q2
Key Milestones
Sep 2023
Company Founded
Bret Taylor (former Salesforce co-CEO, current OpenAI Board Chair) and Clay Bavor (former Google VP, Project Starline) launch Sierra
Feb 2024
Stealth Lift + $110M Series A
Sierra exits stealth at $1B valuation; first customers (WeightWatchers, SiriusXM, Sonos, ADT) revealed
Aug 2024
AgentOS Launch
Sierra's platform for building, deploying, monitoring conversational agents in regulated and high-CX verticals
Oct 2024
Series B at $4.5B
Greenoaks leads $175M, 4.5x the Series A valuation in 8 months
Feb 2025
Voice Agents GA
Native voice support added; targets phone-channel customer service in addition to chat
Aug 2025
Sierra Benchmark + TAU 2.0
Open-source benchmark for evaluating agent quality; standardizes how Sierra customers measure ROI
Oct 2025
Series C at $10B
Per The Information; 2.2x the Series B valuation, ~24 months from founding to decacorn
Nov 2025
$100M ARR
Crosses $100M annualized revenue seven quarters after launch
May 2026
Series D at $15.8B
$950M co-led by Tiger Global and GV; claims more than 40% of the Fortune 50 as customers
Updated at 2026-Q2