Purpose This paper aims to investigate the relationship between corporate governance (CG) and corporate social responsibility (CSR) disclosure in a sample of 64 companies listed on the Tehran Stock Exchange. Design/methodology/approach This study opts for a descriptive-correlational method. To measure the extent of CSR disclosure and CG variables, companies’ annual reports and websites during 2014-2015 are content analyzed by applying a 64-item checklist. Boards’ size, age, tenure and independence, CEO duality, audit committee (AC) composition and ownership concentration are considered as CG variables. To ascertain the CG–CSR disclosure relationship, multivariate linear regression analysis is incorporated. Findings Based on the results, audit committee composition, board tenure and ownership concentration positively influence CSR disclosure level with ownership concentration as the most influential variable, that is, in companies with majority shareholders ownership, managers tend to disclose more CSR information. Research limitations/implications Only annual reports and company websites are analyzed. Researchers are encouraged to apply other methods such as interview and to consider other variables, such as board diversity, proportion of female members and the extent of shareholders activities, to measure CG. Practical implications This paper provides implications at the policy level to identify governance mechanisms to increase CSR awareness of heavy-pollution industries in developing countries. Originality/value Studies rarely examined CSR reporting in Iran, particularly among heavy-pollution companies. Besides, the paper highlights the role of majority shareholders and non-executive AC members in CSR disclosure.