Senior Machine Learning Engineer

Founding Senior Machine Learning Engineer

Join to apply for the Founding Senior Machine Learning Engineer role at Retell AI.

Base pay range

$200,000 – $280,000 per year

About Retell AI

Retell AI is using first principles to reimagine the call center with cutting‑edge voice AI. We believe voice is still the most natural way humans communicate, yet it has been trapped in outdated call centers for decades. Our mission is to bring intelligence, empathy, and speed to every phone conversation between businesses and their customers.

Since launching 18 months ago, thousands of companies now use Retell’s AI voice agents to handle sales, support, and logistics calls that once required large teams of human agents. Backed by Y Combinator, Altman Capital, and other leading investors, we have scaled to $30M ARR with a team of 20 people, up from $5M at the start of 2025.

Now, we’re scaling fast, and we’re looking for bold, ambitious people to help us build the gold standard for voice automation. If you want to work on deeply technical challenges, move fast, and make an outsized impact at one of the fastest‑growing Voice AI startups in the world, you’ll love it here.

Let’s build the future of voice automation together.

• We’re a top 50 AI app in a16z list : https : / / tinyurl.com / 5853dt2x
• We're also one of the top ranking startups on : https : / / leanaileaderboard.com /

About the Role

This is a hands‑on, high‑ownership role for ML engineers who want to build production models that actually ship and perform under real‑world constraints. As a Founding Senior Machine Learning Engineer at Retell, you’ll work across the ML stack to power human‑like voice agents that handle millions of real‑time phone conversations. You’ll fine‑tune large language models and audio models, evaluate them with rigorous benchmarks (and human feedback), and deploy them into latency‑sensitive, high‑traffic systems. You’ll own model performance end‑to‑end—from training pipelines to post‑deployment monitoring—and shape our ML strategy alongside the founding team. If you’re excited by hard technical challenges, fast iteration, and the opportunity to define how voice AI works at scale, this role is a rare chance to do it from the ground up.

Key Responsibilities

YOU MIGHT THRIVE IF YOU

JOB DETAILS

Other Benefits

Compensation Philosophy

$1M revenue / employee, and significant equity.

INTERVIEW PROCESS

Onsite / Virtual Interviews (3 hrs) : Hosted in our office if located in the Bay Area or virtual, with three rounds :

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