Minimizing unwanted catches is a major milestone for achieving sustainable fisheries. In the framework of the Common Fisheries Policy, a landing obligation is being established progressively in European waters (Article 15, EU Regulation 1380/2013). Supplementary management measures have been proposed to support and enhance the effectiveness of this new regime. In this context, the effect of the landing obligation on a demersal mixed fishery (coastal and trawl fleet) in the Aegean Sea (NE Mediterranean Sea) was assessed in terms of both biological and economic sustainability. Our results show that the landing obligation alone does not ensure sustainable fisheries. Management action should be directed to the introduction of additional measures. Evidence suggests that improving selectivity and protecting the nursery grounds are possible solutions to decrease discards and ensure sustainable fisheries in the long term. The landing obligation can have a role in incentivizing the adoption of these management measures that ensure lower fishing mortality on juvenile fish.