Climate change is one of the most pressing issues of this century. Due to the urgency of the issue and the pressure on governments to act, the debate on climate change is moving quickly from the political level to focused conversations on policy choices and implementation options. This background paper discusses the role of competition policy and enforcement in supporting and incentivising sustainable and pro-competitive business practices. It analyses the practical approaches that competition authorities may take when assessing cases with an environmental dimension. It was prepared as a background note for a discussion held at the OECD in December 2021 on environmental considerations in competition enforcement.