The present Ph.D. thesis addresses the role of CSR rating agencies in the institutionalization and standardization of the CSR field. Chapter 1 investigates the idea of fields, which form around issues, and describes the roles of various stakeholders in structuring, shaping, and legitimating of the emerging CSR field. Chapter 2 theorizes the multilevel institutional dynamics of CSR standardization by focusing on the case of CSR rating agencies. The findings make a threefold contribution to the study of organizational standardization and CSR by shedding light on the ways in which environmental, social and governance issues are materialized and translated into figures used by market actors, describing the three core tensions faced by CSR rating agencies at each level of analysis, and bridging CSR standardization dynamics across levels of analysis. Chapter 3 explores the consolidation of the CSR rating industry and provides a detailed examination of the motivations and impacts of consolidation.