Do green bond issuers become cleaner than mixed issuers?

This thesis examines whether publicly listed non-financial firms that issue both conventional and green bonds (“mixed issuers”) differ from firms that issue only green bonds (“pure issuers”) in their environmental performance trajectories, and what this implies for the credibility of green bond issuance. Using a global sample of listed issuers identified through LSEG data over the period 2019–2024, the study combines bond-level information with issuerlevel environmental and ESG indicators. Firms are classified according to whether their screened bond portfolios contain only green bonds or both green and conventional bonds. Environmental performance is assessed through changes in environmental pillar scores, absolute Scope 1 and 2 emissions, and emissions intensity. The empirical analysis combines descriptive statistics, group-comparison tests, and regression models with country and industry fixed effects. Across all main indicators, pure issuers display more favorable environmental trajectories than mixed issuers. On average, they show stronger improvements in environmental scores, greater reductions or smaller increases in emissions, and more favorable changes in emissions intensity. Although statistical significance varies across specifications due to limited effective sample sizes and incomplete ESG coverage, the pattern of results is directionally consistent and economically meaningful. Interpreted through legitimacy theory, these findings indicate that firms combining green and conventional bonds face a greater risk of a credibility gap between sustainable finance claims and underlying environmental outcomes. While the study does not directly trace the allocation of proceeds and therefore cannot identify project-level greenwashing or misallocation of proceeds, it provides suggestive issuer-level evidence that mixed issuers, as a group, lag pure issuers in environmental performance. The thesis therefore makes a substantive contribution to the literature on green bond credibility by showing that the environmental outcomes associated with green bond issuance depend not only on whether firms issue green bonds, but also on how those bonds are embedded within the issuer’s broader financing strategy.