National authorities in many countries advise their populations to eat more seafood, for health and sometimes for environmental purposes, but give little guidance as to what type of seafood should be consumed. The large diversity in species and production methods results in variability both in the nutritional content and in the environmental performance of seafoods. More targeted dietary advice for sustainable seafood consumption requires a better understanding of the relative nutritional benefits against environmental costs of various types of seafood. This study analyzes the combined climate and nutritional performance of seafood commonly consumed in Sweden, originating all over the world. Nutrient density scores, assessed by seven alternative methods, are combined with species- technology- and origin-specific greenhouse gas emission data for 37 types of seafood. An integrated score indicates which seafood products provide the greatest nutritional value at the lowest climate costs and hence should be promoted from this perspective. Results show that seafoods consumed in Sweden differ widely in nutritional value as well as climate impact and that the two measures are not correlated across all species. Dietary changes towards increased consumption of more seafood choices where a correlation exists (e.g. pelagic species like sprat, herring and mackerel) would benefit both health and climate. Seafoods with a higher climate impact in relation to their nutritional value (e.g. shrimp, Pangasius and plaice) should, on the other hand, not be promoted in dietary advice. The effect of individual nutrients and implications of different nutrient density scores is evaluated. This research is a first step towards modelling the joint nutritional and climate benefits of seafood as a concrete baseline for policy-making, e.g. in dietary advice. It should be followed up by modelling other species, including environmental toxins in seafood in the nutrition score, and expanding to cover other environmental aspects. •The climate and nutritional performance of 37 seafood products is assessed.•Seven methods to calculate the nutrient density of seafoods are evaluated.•Variability across seafoods is large both within and between seafood groups.•Most seafoods (21 out of 37) are more nutritious than beef, pork and chicken.•Seafoods with the lowest climate impact and highest nutritional score (e.g. sprat, herring, mackerel and perch) should be promoted in dietary advice.•Nutrition score and climate impact do not correlate consistently across species.