The UK seafood supply chain's heavy reliance on international trade, with 81% of consumption imported and 70% of production exported, creates vulnerability to global disruptions. While COVID-19 impacts on seafood production are well-documented, the processing sector remains under-researched despite its vital role connecting producers to consumers. This paper examines how UK seafood processing businesses responded to COVID-19 and Brexit disruptions, focusing on flexibility, diversity, and connectivity as key characteristics of resilience. We conduct semi-structured interviews with shellfish companies, fish processors, mixed seafood processors, and industry experts across the UK. We find that during the crisis, UK processors demonstrated flexibility through proactive management, financial stability, and rapid business model pivoting. Businesses with diversified products, customers, labour force, and suppliers showed greater resilience. Local social capital and digital connectivity also strengthened responses, whilst severed international connections particularly challenged export-dependent shellfish processors. To build adaptive capacity, we recommend strengthening industry forums to support geographically isolated processors, developing UK processing capacity to reduce dependence on overseas supply chains, and expanding digital infrastructure for direct-to-consumer sales to counteract future disruptions from labour shortages, consolidation in aquaculture, and volatile export markets. This paper makes a theoretical contribution by further refining conceptualisations of resilience in the context of seafood systems and by characterising three firm-level antecedents for adaptations. It also highlights the relational nature of resilience noting that resilience for one business may not increase the resilience of the system as a whole.