Nature-based solutions (NBS) have become an increasingly popular strategy to adapt to flood risks. NBS are often framed as no-regret measures with benefits to natural and social systems. However, questions on how to address social vulnerability and inequality through NBS remain underexplored. This chapter aims to illustrate this through an ex-nunc evaluation of the development of a flood retention area designed as an NBS in an exemplary case in Belgium. Residents were involved in the design of area through co-creation processes. This chapter explores to what extent the flood retention area does not only increase the buffering capacity of the water system, but also reduces social vulnerability to floods. By bringing in perspectives of stakeholders involved in the development of the project, the chapter reflects on the perceived social benefits and pitfalls of NBS from a sustainability perspective, i.e., the extent to which NBS integrate economic, ecological, and social considerations. It is illustrated that although co-creation processes were organized for the design of the NBS, these processes may remain partly symbolic as the primary objectives for the area had been established beforehand by the project initiators. Furthermore, landowners’ interests are overprotected in Flemish spatial planning policies. They have the power to block land-use changes needed to preserve open space for the implementation of NBS. At the same time, the interests and needs of vulnerable communities are not actively considered in the development of NBS, because these projects are often initiated by engineers. These issues may complicate the development of just and inclusive NBS for flood risk management (FRM).