Environmental, social and governance (ESG) rating agencies, as non-financial data providers, have become a central actor in the field of responsible investment. Although research has explored the construction of ESG metrics, little is known about how agencies evaluate decent work. Building on the analysis of six rating agencies, this paper investigates how these actors measure and assess companies on decent work-related items and identifies the challenges they face in this endeavour. The paper aims to better understand the capacity of responsible investment and ESG ratings in promoting and improving decent work within companies.