At first blush, debt-for-nature swaps seem to provide win-win solutions to the looming problems of environmental degradation and extreme poverty. So, one might naturally assume that they are morally permissible, if not obligatory. This article will argue, however, that debt-for-nature swaps are sometimes morally questionable, if not morally impermissible. It suggests that some criticisms of traditional (economic) conditions placed on loans to poor countries also apply to the (environmental) conditionality implicit in such swaps. The article's main theoretical contribution is to suggest a general argumentative strategy for posing a challenge to the moral acceptability of many seemingly innocuous, or even apparently good, policies in the real world. Its discussion of how we should respond to seemingly tragic dilemmas (e.g. between protecting nature and respecting human rights) may also be of general interest.