Seafood consumption and dietary intake of n-3 polyunsaturated fatty acids (PUFA) protect from cardiovascular disease, muscle wasting and mortality; however, their role in delaying unhealthy ageing is uncertain.A prospective cohort study with 1592 community-dwelling individuals aged ≥60 years recruited in 2008-2010, and followed through 2015. Intake of seafood and n-3 PUFA [eicosapentanoic acid (EPA) and docosahexanoic acid (DHA)] was estimated using a validated diet history and food composition tables. Unhealthy ageing was assessed across the domains of physical and cognitive function, mental health, morbidity, self-rated health and vitality.Higher blue fish consumption was negatively associated with unhealthy ageing in 2015 [multivariate ß (95% confidence interval) per interquartile range (IQR) increase of fish: -0.49 (-0.90; -0.08)] and, specifically, was associated with lower accumulation of functional impairments [-1.00 (-1.71; -0.28)] and morbidities [-0.30 (-0.73; 0.13)]. Individuals with high intakes of EPA (≥0.47 g/day) and DHA (≥0.89 g/day) presented the highest reductions in age-related deficits accumulation: -1.61 (-3.01; -0.22) and -1.34 (-2.76; 0.08), respectively. Intake of EPA and DHA were negatively associated with the accumulation of functional deficits [results per IQR increase: -0.79 (-1.64; -0.06) and -0.84 (-1.67; -0.01), respectively] and morbidities [-0.60 (-1.10; -1.11) and -0.60 (-1.09; -0.11)]. No associations were observed between n-3 PUFA and self-rated or mental health, or between white fish and unhealthy ageing.In this cohort of Spanish individuals with elevated intake of fish and a high adherence to the Mediterranean diet, consumption of blue fish and n-3 PUFA had a prospective protective association with deficits accumulation.