Purpose: The purpose of this thesis is to investigate ways of improving sustainable sourcing. The focus of this thesis is to identify what data should be collected, the most appropriate ways of gathering it, and how it can be used to improve sustainable sourcing in large and global companies. The objective is to provide insights on how large companies can take informed decisions to address sustainability within their suppliers' operations and their own sourcing practices generally, by investigating supplier specific data.  Method: The approach taken for this research was to conduct an exploratory single case study in a large and global retail company. Furthermore, all three research questions were answered using qualitative methods, which include interviews and analysing documents from the case company. Findings: In this study, it was found that to improve sustainable sourcing, companies should collect data on suppliers’ performance in economic, environmental, and social sustainability and their ability to be transparent and trace the flow of raw materials in the supply chain. Companies can collect data from upstream supply chains through audits, using traceability and transparency tools, and obtaining a chain of custody for all raw materials. Moreover, companies can utilise the collected data for efficient and effective resource allocation, managing supply relationships and planning, and supplier development. Implications: This thesis contributes to existing research within the field of sustainable sourcing as it features a new approach on how to improve current practices by considering the data that should be collected from suppliers. Moreover, it broadens the perspective by featuring sustainable sourcing specifically in the context of a large and global company. The practical implications of the study address how practitioners can improve sustainable sourcing. The implications include bringing awareness to a possible disconnection between the economic criteria and the other dimensions of the triple bottom line, the limitations of exclusively relying on in-house auditing, and a narrow focus on a limited number of raw materials.   Delimitations: This thesis is limited to a single case study of a large and global company. The data discussed in the thesis focuses on data collected from first-tier suppliers; data collected further upstream or downstream from the case company is outside of the scope of the study.