The study examines the relationship between internal controls and environmental sustainability disclosure on the firms listed at the Nairobi Securities Exchange. The study period was (5) years (from 2013 to 2017). It employed a correlational survey research design covering the period of five (5) years (2013 - 2017). The target population was sixty-five (65) firms listed at the NSE, with a sample size of 56 firms. Data was utilised from firms’ annual reports, stand-alone reports, and website. Pearson’s correlation, Ordinary Least Square regression model and Environmental Disclosure Index were used in analysis. The study findings indicated that R² = 0.64 with audit committee independence (β= .12, p< .05) having a positive and significant effect on envirnonmental sustainability disclosure. More findings showed that financial strength strengthen the relationship between environmental sustainability disclosure and audit committee independence (β = .13, ρ<.01). The inclusion of the interaction term resulted in an R² change of 0.09 (internal controls*financial strength). The study concluded that, overall, financial strength has significant moderating effect on the relationship between corporate governance and environmental sustainability disclosure. It recommends;enactment of policies addressing corporate environmental reporting by firms as a result of different asset base, establishment of corporate environmental committee to spearhead ecological issues, and implementation of mandatory disclosures.