Lead Machine Learning Engineer - AI Agents

Upwork ($UPWK) is the world’s largest work marketplace, connecting businesses with highly skilled professionals worldwide. From entrepreneurs to Fortune 100 enterprises, companies trust Upwork’s platform to access expert talent, leverage AI-powered work solutions, and drive meaningful business outcomes.

Upwork’s AI-powered platform has facilitated over $20 billion in economic opportunity for professionals worldwide. With professionals spanning 10,000+ skills, including AI and machine learning, software development, sales and marketing, customer support, finance and accounting, and more, Upwork empowers businesses of all sizes to scale, innovate, and build agile teams.

We’re looking for a Lead AI/ML Engineer to help shape the future of intelligent systems at Upwork. In this role, you’ll design and deliver cutting-edge infrastructure and models that power agentic LLM workflows across our platform. You’ll work at the intersection of research and production, owning the delivery of advanced ML solutions and driving business outcomes through applied innovation. 

This role offers the chance to lead high-impact projects, support and mentor others, and help shape the future of autonomous AI agents globally. You'll work on cutting-edge machine learning initiatives that drive real business results while contributing to the broader AI research community through publications at leading conferences.

Responsibilities

• Architect and implement core infrastructure to support agent-based LLM systems, including multi-agent pipelines, RAG, and real-time orchestration.
• Train and fine-tune custom models, including LLMs and foundation models, to solve unique Upwork-specific challenges.
• Lead cross-functional collaboration across engineering, product, and research teams to align technical solutions with business impact.
• Mentor and guide engineers and researchers, helping foster a high-performing, inclusive team culture grounded in AI excellence.
• Translate experimental ideas into reliable, scalable production systems by applying best practices in AI engineering and deployment.
• Publish and share innovations where appropriate, contributing to Upwork’s visibility in the broader AI/ML research community.
   

What it takes to catch our eye

• Strong proficiency in Python and modern ML frameworks such as PyTorch or TensorFlow, with experience developing and deploying AI systems.
• Deep understanding of core ML concepts, including transformers, generative models, and agent architectures such as MCP or A2A.
• Experience training large models on GPU clusters and integrating LLMs with external tools via APIs or orchestration frameworks.
• Comprehensive understanding of foundational deep learning, machine learning concepts, and state-of-the-art GenAI models.
• Hands-on experience training custom LLMs on GPUs and working with Retrieval-Augmented Generation (RAG) systems.
• Proven ability to build end-to-end ML pipelines—from data prep and experimentation to production deployment—in a cloud-native environment.
• A growth mindset, strong communication skills, and the ability to translate complex technical work to stakeholders across functions.
• Demonstrated experience working in R&D environments; publications in major AI/ML conferences are a plus, but not required.

Come change how the world works.

At Upwork, you’ll shape the future of work for a global, remote-first workforce, creating economic opportunities for professionals worldwide. While we have a physical office in Palo Alto, we currently hire full-time employees in 21 U.S. states, making it easier than ever to join our mission from wherever you call home.

Our culture is built on trust, risk-taking, customer focus, and excellence, all in service of our core mission: to create economic opportunities so people have better lives. We embrace authenticity and inclusion, encouraging everyone to bring their whole selves to work. Personal and professional growth is a priority here, supported through development programs, mentorship, and our Upwork Belonging Communities.

We’re proud to offer benefits that go beyond the basics, including comprehensive medical coverage for you and your family, unlimited PTO, a 401(k) plan with matching, 12 weeks of paid parental leave, and an Employee Stock Purchase Plan. Visit our Life at Upwork page to learn more about our values, working principles, and the overall employee experience.

Ready to help shape the future of work? Check out our Careers page and follow us on LinkedIn, Facebook, Instagram, TikTok, and X to learn more about life at Upwork.

Upwork is an Equal Opportunity Employer committed to recruiting and retaining a diverse and inclusive workforce. We do not discriminate based on race, religion, color, national origin, gender (including pregnancy, childbirth, or related medical conditions), sexual orientation, gender identity, gender expression, age, status as a protected veteran, status as an individual with a disability, genetic information, or other legally protected characteristics under federal, state, or local law.

Please note that a criminal background check may be required once a conditional job offer is made. Qualified applicants with arrest or conviction records will be considered in accordance with applicable law, including the California Fair Chance Act and local Fair Chance ordinances.