Purpose – The aim of this study is to investigate the role of sustainability governance on sustainability assurance quality. The authors examine both firm-level and country-level variables. Design/methodology/approach – The samples are 1, 168 firm-years from 19 emerging countries with periods from 2017 to 2023. Sustainability assurance quality was assessed through content analysis of assurance statements. Firm-level variables include sustainability performance, board characteristics and assurance providers’ characteristics. The authors include SDG score, environmental performance index and world governance indicators for country-level variables. Findings – The authors found that board size, board attendance and board independence are positively associated with sustainability assurance quality. The authors found positive associations between all country-level variables and sustainability assurance quality. The authors found little evidence of the positive effect of board gender diversity. However, the authors failed to document a significant positive effect of the presence of the sustainability committee and assurance providers’ characteristics. Originality/value – The authors have not found extant studies examining sustainability governance, encompassing both firm-level and country-level factors, in the context of emerging countries. Given the relatively weak legal enforcement in those countries compared with developed countries, assessing sustainability assurance quality within this setting provides critical insights and addresses a gap in the existing literature. © 2025 Emerald Publishing Limited