In this chapter we introduce the topic of moral uncertainty, argue that moral uncertainty is a real and significant issue, and argue that there are non-trivial answers to the question, ‘Given that we are morally uncertain, how ought we to act in light of that uncertainty?’ In particular, we argue that there is an answer to the question of what a morally conscientious agent rationally should do when she is morally uncertain. We shall also consider and defend against some recent objections to the very project of trying to develop an account of decision-making under moral uncertainty: we’ll call these the fetishism objection; the regress objection; the blameworthiness objection; the conscientiousness objection; and the disanalogy with prudence objection.