Guedes,Maria João CoelhoRoux, Amélie2026-06-022026-06-022026http://hdl.handle.net/10400.5/118894Trabalho Final de Mestrado, Management, ISEG, 2026.Environmental, social, and governance (ESG) factors have become central to corporate strategy and investor decision-making. Increasingly, ESG considerations influence deal selection, valuation, and integration, positioning them as critical drivers of Mergers and Acquisitions (M&A) outcomes. This thesis examines how ESG ratings respond to M&A by analysing Salesforce’s 2021 acquisition of Slack, through an ESG measurement lens, using provider ESG rating time series and complementary disclosure and media evidence to contextualise rating dynamics and divergence. Drawing on ESG rating data from Bloomberg, Morgan Stanley Capital International (MSCI), and Sustainalytics for the period 2016–2025, complemented by sustainability reports and media coverage, the study investigates whether the acquisition produced measurable short-term changes in Salesforce’s ESG ratings and how rating divergence manifests at the firm level. The results show no evidence of an ESG rating “jump” after the acquisition. Instead, all three providers display stable or gradually improving trends, while their assessments diverge considerably, consistent with prior research on low inter-rater reliability. These findings suggest that ESG-aligned deals do not automatically translate into higher ratings and that methodological heterogeneity continues to shape how acquisitions are evaluated. The observed stability may reflect strategic consistency: sustaining ESG performance through integration can enhance legitimacy and support long-term credibility, highlighting ESG in M&A less as a source of immediate rating gains and more as a mechanism for sustaining institutional trust.application/pdfengESG ratingsmergers and acquisitionsinter-provider rating divergencesignaling theorySalesforce–Slack acquisitionmaster thesishttp://hdl.handle.net/10400.5/118894