This article examines the legal operation and impact of legal custody presumptions. We compare the nature of joint legal and joint physical custody and explore common misunderstandings about how presumptions work and their practical repercussions for children and parents. We conclude that legal custody presumptions are not suited to the task of promoting quality decision making and healthy parent–child relationships and they recommend alternative approaches. Key Points for the Family Court Community: The operation and impact of legal custody presumptions are often misunderstood by practitioners. The goal of quality decision making on behalf of children is more realistically achieved through other approaches.