Eco-labelling is a way to promote sustainable development. This is a quantified study about purchase behaviour regarding eco-labelled seafood in Sweden, based on interviews with a convenience sample of consumers in situ. The objectives were to establish how large the knowledge of eco-labelled seafood is, to investigate the reasons for acquiring the product and thus determine the prime driving force to do it. The willingness to pay for eco-labelled seafood was also investigated. The results show a low awareness where just about a quarter of the respondents knew that eco-labelled seafood existed. The willingness to pay was high; four out of five were ready to spend additional money on an eco-labelled product. Women displayed a higher willingness to pay than men, which supports previous research. Regarding the reasons to purchase the only options presented to the respondents were environmental concern, enhanced health or both alternatives in combination. Health as the single factor was the least preferred choice and the two other alternatives were favoured to an equal amount. A difference in purchase behaviour can be detected among respondents with awareness of ecolabelled seafood when compared to those without. Those aware stated a willingness to pay to a higher degree and also displayed more environmental concern and less health interest than those unaware of eco-labelled seafood.