© 2020 John Wiley & Sons Ltd Consumers are being encouraged to choose sustainable seafood. In particular, eating less-popular, under-utilized species is promoted as a more sustainable seafood choice. This message is advocated in the media by a range of different organizations and individuals; however, evidence of greater seafood sustainability as a result of these messages is lacking. We examine current media messaging around sustainable seafood, focussing on the messages to eat more under-utilized species, in an Australian and international context. We identify six different intended outcomes of these messages, including that eating more under-utilized species will take pressure off heavily fished stocks, and explore the conditions under which the perceived outcomes would be realized. We use an economic lens and discuss the effect of certain aspects of consumer demand and seafood product substitutability. We propose that in order to take pressure off overfished stocks, the message to consume more under-utilized species would need to be accompanied by messages to limit or eat less seafood. In addition, the benefits of eating more under-utilized species as currently promoted are not always achievable and that the outcomes of some messages, if realized, could lead to overfishing of unregulated stocks and a reduction in overall fish supply. While there are many potentially positive social, economic and environmental outcomes of consuming currently under-utilized species, media messages should encourage consumers to buy a range of seafood, including under-utilized species, which can be traced back to a well-managed fishery, rather than promoting under-utilized species per se.