<p>Among the most significant challenges associated with the full transition to a more sustainable financial market is the disagreement regarding ESG ratings. Although researchers have examined this phenomenon by assessing its determinants and potential effects, the existing literature remains fragmented. Therefore, we conduct a systematic literature review of 101 peer-reviewed articles published between 2018 and 2025 to categorise the most relevant papers on this topic according to their methodological approaches. We further categorise them according to the theoretical and analytical perspectives used to assess disagreement, such as determinant, effect, or other perspectives. The results show that many articles use quantitative methods and analyse the consequences of disagreement. By contrast, the literature on determinants primarily evaluates the different rating methods and discrepancies in reporting standards. The study highlights conceptual and methodological gaps that make it difficult to compare ESG metrics. It also suggests possible avenues for future research by analysing these patterns. The findings contribute to advancing theoretical understanding and offer practical insights for investors, rating agencies, and policymakers engaged in the development of credible sustainability assessment frameworks.</p>