I attempt to resolve the question of whether keeping animals as pets is akin to slavery by considering the significance of liberty to human beings and to nonhuman animals. I distinguish between two senses of liberty: preference liberty and autonomous liberty. Preference liberty is the freedom to satisfy the preferences that one in fact has. Autonomous liberty is the ability to satisfy the preferences that one might have regardless of whether one actually has those preferences. Preference liberty has a value for animals, but autonomous liberty is meaningless for them. As the core wrong of slavery is the restriction of autonomous liberty, I conclude that pet-keeping is not akin to slavery, though in practice it is often morally wrong for other reasons.