Seafood is the most internationally traded food product, yet its supply chains remain fragmented, with inconsistent traceability systems hindering verification of sustainability, legality, and authenticity. In response, the EU-funded FishEUTrust project aims to build trust, transparency, and sustainability in European seafood supply chains through several tools integrated into a centralized, interoperable digital platform. This paper presents the development of a digital product passport prototype tailored to seafood, providing end consumers with reliable information from the platform about origin, supply chain conditions, nutritional value, and environmental impact. The passport integrates lifecycle data for the batches of seafood, measurements from sensors and external platforms, expert knowledge-based interpretation of data, and blockchain-based change tracking to ensure data integrity. Real-world testing is conducted via five Living Labs across Europe, engaging stakeholders from aquaculture to retail. The platform helps consumers make informed choices, increases transparency and accountability in the supply chain, and supports the EU’s digital and sustainability objectives.