Environmental failures associated with mining operations are persistent issues. It is therefore surprising that we still know very little about whether companies are taking the organisational steps necessary to reliably achieve acceptable environmental performance. Companies use sustainability reports to describe their progress towards fulfilling environmental commitments. This study examines sustainability reports published by seven of the largest mining companies through the lens of High Reliability Organisation (HRO) theory and considers what those reports reveal about the reliability of mining company environmental activities. We conclude the extent to which environmental management practices align with HRO characteristics cannot be determined with certainty from sustainability reports. The data does suggest an insufficient embedding of environmental management in organisational collective mindsets, as well as other significant gaps in the application of HRO hallmark characteristics to environmental activities. Alternative data sources need to be explored to determine the reliability of environmental management in practice.