The 2018 Nigerian Code of Corporate Governance demands responsible behaviour and environmental sensitivity from all companies in Nigeria. However, the extent of environmental reporting amongst firms in Nigeria is still low and not a listing requirement despite the trend of disclosure practices by firms around the world. As a step towards addressing this shortcoming, the objective of this paper is to examine the effect of diversity-of-board on environmental reporting of listed manufacturing companies in Nigeria, and further explores the moderating effect of audit committee. Board size, Board independence and directors share ownership was used as a composite index to proxy for Diversity-of-board and Environmental reporting was graded using ISO14031 index. The study has a population of 61 listed manufacturing firms and a sample size of 36 firms which was arrived at using stratified sampling criteria. Through content analysis, secondary data was collected from the annual report of the sampled companies from the period 2002 to 2019. Using descriptive statistics and linear multiple regression, findings from this study revealed that before moderation, diversity-of-board has no significant effect on environmental reporting (t= -1.80, P˂ 0.001). However, the study found that audit committee significantly moderates the effect of diversity-of-board on environmental reporting (t= -3.67, P˂ 0.001). Since the moderating effect of audit committee on diversity-of-board and environmental reporting is negative the study concludes that both diversity-of-board and audit committee do not strengthen environmental reporting. The study recommended that the financial reporting council of Nigeria should include environmental committee as one of the mandatory committee in the code of corporate governance who will specifically handle environmental issues.