Abstract To facilitate Safe-and-Sustainable-by-Design (SSbD), the HARMLESS project developed a SSbD approach and Decision Support System (DSS) for advanced materials. The SSbD approach and DSS are in alignment with the EU recommended SSbD framework, tools and methods, including New Approach Methodologies (NAMs), and tailored to the innovation stage of the material under development. The SSbD approach follows a flexible stage-gate model with three innovation stages: 1) Ideation & Business Case Phase, 2) Lab Phase, and 3) Pilot Phase. The SSbD-DSS guides designers through a workflow starting with the Advanced Material Earliest Assessment (AMEA) tool. AMEA contains three questions enabling categorization and subsequently advice on design principles. A second tool, named Warning flags, design Advice, Screening Priorities (WASP) consists of twelve questions to identify early warning flags and provide design and assessment advice. A third tool, named Alternative SSbD Design Inspector (ASDI) provides guidance on descriptors to measure in the Lab Phase for informed decision making on the most optimal SSbD version. By adapting the data and resource requirements to each innovation stage, the SSbD-DSS facilitates practical implementation of SSbD, supporting the user to find a transparent balance between safety, sustainability and performance.