Office and HR assistant - Amsterdam Office

Your mission

As Office & HR Assistant, you make sure things run smoothly in our Amsterdam office.

You handle day-to-day HR administration, keep the office in good shape, and support the CEO with coordination when needed. You are often the first point of contact for employees and help ensure that onboarding, requests, and daily operations are handled properly.
This is a part-time role (20 hours per week), ideally suited to someone who enjoys bringing structure and continuity to a growing startup. Much of the work is predictable, allowing you to organize your time effectively while remaining flexible during occasional busier periods.
This is a hands-on, service-oriented role. Much of the work happens in the background, but it makes a real difference to how the team operates. We are today a team of around 20 people in Amsterdam which is expected to grow.

In this role you will:

In general, the work is often interrupt-driven It is primarily service-oriented, supporting others to perform. Much of the impact is invisible, but essential to how the organization functions. You follow existing processes, and improve them where relevant. You escalate topics that impact payroll or require validation. You are able to prioritize employee requests, while aligning with leadership needs
HR Support & Employee Experience

• Monitor HR, recruitment, and general inboxes, and route or respond to requests as appropriate
• Coordinate onboarding (documentation, office setup, HR system entry)
• Support administrative HR processes, including invoices and pension-related tasks (reviewing monthly statements and flagging discrepancies)
• Act as a first point of contact for employees in Amsterdam on HR questions, escalating when necessary
• Help organize internal events such as team gatherings, offsites, and Town Halls

Office Operations

• Oversee the daily functioning of the Amsterdam office (supplies, equipment, general readiness)
• Ensure the office remains in good working condition and is ready for employees and visitors
• Liaise with the building landlord and property management as the main contact
• Support basic health and safety and compliance requirements

Executive Support

• Provide agenda and scheduling support to the CEO
• Assist in coordinating meetings with internal and external stakeholders
• Support the CEO’s LinkedIn presence (drafting posts, managing interactions as needed)
• Help ensure professional and seamless experience for visitors and external partners

Administrative Support

• Coordinate meetings, travel, and logistics for leadership team members when required
• Prepare agendas, take notes, and transcribe meeting outputs when needed
• Support documentation and follow-up to help keep priorities aligned and visible

About you:

You are someone who keeps things running without needing constant direction. You notice what needs attention and take care of it.
You work in a reliable and discreet way, with a practical, service-oriented mindset. You communicate clearly and know how to adapt depending on who you are dealing with.
You are comfortable in an environment where not everything is fully defined, and where priorities can shift during the day.

This role suits someone experienced who is looking for a part-time position with real responsibility, and who takes satisfaction in making things work smoothly for others.

• Around 3+ years of experience in Office Management, Executive Assistance, Operations, or a similar role
• Experience in a scale-up or fast-paced environment is an advantage
• Good working knowledge of Microsoft 365 (Word, Excel, PowerPoint, Outlook)
• Experience with travel booking and expense tools
• Native Dutch and fluent English (C1/C2) are required
• French is a plus
• Ability to move between operational tasks and executive-level support without losing track of either

What you can expect from us:

• The opportunity to help realize the most promising reactor technology and advance Europe's energy future
• Being part of an exceptional team that combines engineering rigor, scientific excellence, and entrepreneurial drive
• Working in multidisciplinary teams on ambitious missions, with responsibility and meaningful impact from day one
• A fast-moving deep-tech environment where initiative is valued and people are trusted to make decisions
• Complex, multidisciplinary challenges that will stretch you and accelerate your growth
• Competitive compensation and participation in our employee profit-sharing plan
• An international workplace with offices in the heart of Amsterdam and Lyon

About us

At Thorizon, we’re a passionate team spread across Amsterdam and Lyon, all working together to develop new nuclear power solutions. We design and create frontier technology for Molten Salt Reactors (MSRs).

Our purpose is to accelerate the availability of clean energy and help solve the climate crisis.

We are in the development phase and aim to solidify our design through analyses, simulations, experiments, prototyping, and partnerships. At Thorizon, we believe a strongly coupled multidisciplinary technology development requires a culture of full openness and transparency. That’s why we foster values like unity, communication, and support to ensure we grow together as a team while achieving our purpose.