Cresta vs Sierra AI (2026)
Comparing Cresta and Sierra AI? Both are Voice & Phone AI tools in the directory, which is why buyers put them on the same shortlist. Below is a side-by-side look at pricing and an estimated monthly bill, channels, compliance claims, and integrations, plus when each is the better fit, so you can pick on the facts rather than either vendor's own sales page.
At a glance
| Attribute |
 Cresta
|
 Sierra AI
|
|---|---|---|
| What it is | Real-time agent assist and AI insights for contact centers, trained on your best performers. | AI agent mirrors the nuances of human communication, ensuring seamless and organic customer service interactions while improving customer satisfaction. |
| Pricing | Paid · Custom | Per resolution · Custom |
| Est. monthly cost | No published price to estimate | No published price to estimate |
| Founded | 2017 | 2023 |
| Categories | Agent Assist & Copilots Contact Center & CCaaS QA & Conversation Analytics Voice & Phone AI | AI Agents & Chatbots Enterprise Voice & Phone AI |
| Channels | ||
| Chat | ✓ | ✓ |
| ✓ | ✓ | |
| Voice | ✓ | ✓ |
| SMS | ✓ | ✓ |
| — | ✓ | |
| Compliance (vendor-claimed) | ||
| SOC 2 | ✓ | ✓ |
| HIPAA | ✓ | ✓ |
| GDPR | ✓ | ✓ |
| ISO 27001 | — | ✓ |
| PCI DSS | ✓ | ✓ |
| FedRAMP | — | ✓ |
| ISO 42001 | ✓ | ✓ |
| EU AI Act | — | ✓ |
| Data residency | Not verified | Not verified |
| Languages | 30+ languages | 59 languages |
| What the AI can do | ||
| Takes actions | ✓ | ✓ |
| Hands off to a human | ✓ | ✓ |
| Choice of LLM | Not verified | — |
| Buying | ||
| Free trial | Not verified | Not verified |
| How you buy | Not verified | Not verified |
| Minimum commitment | — | — |
| Company | Independent, venture-backed | Independent, venture-backed |
| Works with | Salesforce Five9 Genesys Amazon Connect NICE CXone Avaya | Salesforce Zendesk Shopify Twilio Stripe Snowflake |
| Key features |
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| Next step |
Full listing Visit site → |
Full listing Visit site → |
Estimates assume 5,000 conversations a month, 60% handled by AI and 10 agent seats, at each vendor's published list price (the cost calculator's model); treat them as a floor, not a quote. Compliance rows are what vendors publicly claim, and “Not verified” means we have not confirmed that fact yet, not that the tool lacks it.
Choose Cresta or Sierra AI?
Choose Cresta if
Best for: Large contact centers on Five9, Genesys, Amazon Connect, NICE or Avaya that want real-time agent guidance learned from their own top performers, plus automated QA, a training simulator and autonomous agents, with SOC 2, HIPAA, PCI DSS and ISO 42001 coverage.
- you need agent-assist copilots for human reps
- you need QA scoring and conversation analytics
- you prefer a flat subscription to usage-based billing
Look elsewhere if you run a small team or want a self-serve product: Cresta sells to serious operations with quote-based pricing and no free trial, and its value depends on having enough conversation volume to learn from.
Choose Sierra AI if
Best for: Large brands that want one branded agent deployed across chat, voice, email, SMS and WhatsApp, with voice agents that can take a payment mid-call, outcome-based pricing, 59 languages and the broadest compliance list in the directory including FedRAMP, ISO 42001 and the EU AI Act.
- you need autonomous AI agents
- you need enterprise scale, security, and compliance
- you need WhatsApp coverage
- you need a vendor that publicly claims ISO 27001, FedRAMP, and EU AI Act
Look elsewhere if you are not an enterprise: Sierra sells multi-year contracts by quote with no trial or self-serve start, and its verified facts do not include a stated data residency.
About Cresta
Cresta started from a simple observation: in every contact center, a handful of agents dramatically outperform the rest, and everything they do differently is sitting in the call recordings. Founded in 2017 by Zayd Enam, Tim Shi, and Sebastian Thrun, the Stanford professor behind Google X and Udacity, Cresta mines those conversations to learn what the best performers do, then coaches every agent in real time: suggested responses, knowledge, and guidance appearing on screen during live calls and chats.
That real-time layer is still the heart of the product, but the platform now spans the full loop. Conversation intelligence gives leaders visibility into every interaction, automated quality management replaces sampled QA scorecards, a training simulator lets agents rehearse against AI customers, and autonomous virtual agents take the high-volume calls that never needed a human. It plugs into the major contact-center stacks, including Five9, Genesys, Amazon Connect, NICE, and Avaya, so it layers onto what you run rather than replacing it.
Cresta sells to serious operations: United Airlines, Alaska Airlines, Cox Communications, Marriott, and Brinks Home are named customers, and investors including Andreessen Horowitz, Sequoia, and Greylock have backed it to the tune of roughly $276 million, most recently a $125 million Series D in late 2024 that valued the company around $1.6 billion. Pricing is enterprise and quote-based, with no public numbers.
Cresta is the pick when your strategy is making human agents better rather than replacing them, especially in revenue-bearing conversations like sales and retention where a slightly better sentence is worth real money. If you want humans out of the loop entirely, look at the autonomous-agent specialists; if you want your hundred agents performing like your best ten, Cresta was built for exactly that.
Read the full Cresta listing → · See Cresta alternatives →
About Sierra AI
Sierra builds conversational AI agents for the enterprise, and it arrived with about as much star power as a startup can carry. It was founded in 2023 by Bret Taylor and Clay Bavor, and if those names ring a bell it is because Taylor co-created Google Maps, served as CTO of Facebook and co-CEO of Salesforce, and currently chairs the board of OpenAI, while Bavor spent eighteen years at Google leading its virtual and augmented reality work. Company lore says the whole thing was hatched over a grilled branzino lunch in Palo Alto.
The product lives up to the pedigree. From a single build, Sierra deploys a branded agent across chat, voice, email, SMS, and even ChatGPT, following your policies, adopting your brand's voice, and escalating gracefully when a conversation gets thorny. Its voice agents are a standout: they hold natural, low-latency conversations, read sentiment, and can even take a credit card or ACH payment over the phone in one uninterrupted call, with no clumsy handoff to a separate system.
Under the hood sits Agent OS, a platform for building, testing, and supervising agents, with tooling to run voice simulations and rehearse behavior before anything reaches a real customer. Pricing is outcome-based, tied to conversations or successful resolutions and wrapped in multi-year enterprise contracts, so Sierra is aimed at large brands rather than weekend experimenters. Reported customers include SoFi, Ramp, and Brex, and the company says its agents already serve a meaningful slice of the Fortune 50.
Sierra's fundraising has kept pace with its towering ambition, vaulting the company into the rarefied tier of the most valuable AI startups in barely two years. For enterprises that want polished, on-brand agents across every channel and are willing to invest the time and budget to do it properly, Sierra is a genuine marquee choice.
Read the full Sierra AI listing → · See Sierra AI alternatives →
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