Retell AI

Senior Machine Learning Engineer

San Francisco Bay Area · Senior

Work authorization required$225k-$325kDetected 279 days ago

PythonBackend DevelopmentMachine LearningPyTorchLLMsA/B TestingNegotiationLogisticsAdaptability

About the role

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.
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.

Benchmark & Evaluate - Build datasets, define rigorous metrics, and measure model performance across high-impact voice AI tasks to guide development.
Run Human Evaluations - Build scalable pipelines to collect structured human feedback, benchmark subjective quality, and inform model iterations.
Level Up Infrastructure - Design and maintain the ML infrastructure needed for fast experimentation, robust training, and continuous deployment.
Clear Communicator & Team Player - You collaborate well across functions and push decisions forward.
Let's build the future together.

Fluent in Modern ML Stack - You know your way around Python, PyTorch, and today's ML tools-from training pipelines to evaluation benchmarks.
Thousands of companies now utilize Retell's AI voice agents to handle sales, support, and logistics calls that once required large teams of human agents.

100% coverage for medical, dental, and vision insurance
$200/month wellness reimbursement (gym, fitness classes, etc.)
$300/month commuter reimbursement (gas, Caltrain, etc.)
$75/month phone bill reimbursement
$50/month internet reimbursement
Our vision for 2026 is to build a modern CX platform where entire contact centers are powered by AI.
Small teams, >$1M revenue/employee, and significant equity.
Bonus if you've worked with LLMs or audio models.
Equity: Offers Equity
ML Question Deep Dive: In-depth discussion exploring your approach to a machine learning problem.

Retell AI is open to sponsoring work authorization for qualified candidates, including H1B/H-1B, TN, L-1, E-3, F-1 (OPT/CPT), and O-1 visas.

This listing is sourced directly from Retell AI's careers page and normalized into a canonical job model.