Can we acquire ethical knowledge on the basis of emotion? One serious barrier to thinking so is that our emotions are highly unreliable guides to ethical truth. They are pervasively influenced by irrelevant factors—above all by the mood the agent happens to be in—which leads to frequent mismatches between our emotions and the ethical landscape. This threatens to render the habit of forming emotion-based ethical beliefs too unreliable to yield knowledge. I develop a new solution to this problem. An agent can develop a capacity of “watchfulness”: of recognizing situations in which her emotions are untrustworthy and withholding judgment. Despite the vicissitudes of her emotions, a watchful agent won’t be prone to forming false ethical beliefs on the basis of emotion. Like a basketball player who knows when to shoot and when to pass, an such an agent can preserve an excellent ratio of shots on target despite having dodgy aim from certain angles. Consequently, her habit of making emotion-based judgments will be reliable and a potential source of ethical knowledge.