The relationship between animal rights and contractarian theories of justice such as that of Rawls has long been vexed. In this article, I contribute to the debate over the possibility of inclusion of animals in Rawls's theory of justice by critiquing the rationale he gives for their omission: that they do not possess moral personality. Contrary to Rawls's assumptions, it appears that some animals may possess the moral powers that comprise moral personality, albeit to a lesser extent than most humans. Some animals can act in pursuit of preferences and desires (and communicate them non-verbally), which might be taken as implicitly selecting a conception of the good; further, scientific research demonstrating inequity aversion and social play behaviors suggests that some animals can have a sense of justice relating to their own social groups. I conclude that Rawls's theory needs to acknowledge any animals that can be considered to meet the threshold of moral personality, while the concept of moral personality as a range property may also require reconsideration.