Anno 2021, designers engage with questions of increasing complexity and impact. Designers are involved in creating services and systems that reach beyond an individual user, ultimately reshaping society. This realisation motivates the question of how designers should deal with the accompanying responsibility. The domain of Design for Values (van den Hoven et al., 2015) encourages conscious innovation with the call for a deliberate design for values and advocates a thoughtful stance towards the creation of artefacts. As social design is concerned with societal well-being and commitment to design for the common good (Tromp, Hekkert, 2017), it is regarded as a specificity of Design for Values. This thesis opens up the conversation of impact in social design practices by researching how designing for values is validated within social design projects. Although the mission for conscious design is vital, frameworks to assess the adequate operationalisation of values are lacking, and impact methodology in the field of social design is fairly under developed. Hence, measures to guarantee value manifestation and safeguard engagement with claims made are missing. For this reason, both domains of Design for Values and social design will be enhanced by a framework that supports assessing the design for value, as a result enabling validation of value realisation within design projects. The Value Validation Framework introduced in this thesis presents the structure of reasoning towards a valid value claim. It is argued that to make a valid claim, designers must specify their value claim in terms of effects on behaviour, substantiate a claim with proper evidence and provide justification for these specifications. This ensures construct validity for the claim being made and above all, that designers discern what they are factually achieving. As a result, the framework administers a critical stance towards the impact that can be ascribed to projects. First, the Value Validation Framework was constructed out of theoretical models enriched with qualitative data from an explorative study among professionals. This framework enabled to assess social design projects and was used in the second part of this thesis, the case study research. In this study, five social design projects are assessed concerning the validity of their claim to realise a particular value with their design. The study provided an increased understanding of how designers structure their design projects and this information was used in the third part of this thesis. In which the analysis was used to reflect on ways to make valid value claims. Social designers involved in the case study research endorse the unique perspective that the Value Validation Framework provides and emphasise that the conducted analysis has provided a meaningful assessment of their social design projects. A commitment to value claim validation provides an opportunity for social designers to enhance their considerations of effect and focus on the substantial impact they accomplish. As a result, contributing to a renewed perspective on how they can enhance their design project and fundamentally commit to a better world.