During the course of the campaign which will last throughout May and June the retailer will stock only sustainable fish.
Selfridges' Oxford Street store will feature collaborations with artists to highlight issues facing the world's oceans. Activity will also be reflected in its Birmingham and Manchester stores and online.
Research suggested that unless the way fish was sourced changed, global stocks would be depleted within the next generation, said Alannah Weston, Selfridges' creative director. Selfridges could help by "making positive choices and using stores creatively as a platform to get people talking about the issues."