Collaborative procurement is increasingly on the policy agenda in many countries, yet problems with collaboration occur. This article adopts a relational theory perspective to explore the enablers of and barriers to collaboration in purchasing, helping identify success factors. The authors adopted a mixed qualitative/quantitative methodology and interviewed 51 senior staffers in the United Kingdom. They found that collaborative public procurement is hindered by local politics and differing priorities, supplier resistance, reliance on suppliers for data, and a lack of common coding systems. Enabling factors for collaborating with local governments include dealing with local issues and buying from small and medium-sized enterprises. For health care providers, important themes are product innovation and ensuring supply. The authors develop a list of enabling factors and show their effect on collaboration success. This may assist policy makers in identifying areas of guidance and help practitioners prevent problems in collaboration.