Purpose: This study examines how tone management in board reports influences corporate social responsibility (CSR) performance in emerging markets, focusing on the Tehran Stock Exchange. It addresses the underexplored qualitative aspects of CSR disclosures, particu- larly how abnormal tone signals transparency or concealment in sustainability reporting. Design/methodology/approach: This paper is based on a postgraduate study completed in 2022. Using a dataset of 987 firm-year observations (2016–2022), we measure abnormal tone through textual analysis of board reports and assess its impact on six CSR dimensions. The methodology combines vocabulary-based tone detection with regression analysis, controlling for firm-specific factors. Findings: The results reveal a significant negative relationship between abnormal tone and CSR performance, particularly in environmental and energy dimensions. The adverse effects persist into subsequent years, highlighting the long-term consequences of tone manipulation. Originality/value: This study contributes to the social and environmental accounting literature by analysing tone management in an emerging market context. It introduces vocabulary combinations as a novel approach to detecting nuanced tone variations, offering practical insights for regulators and firms aiming to enhance CSR transparency.

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