Although the vast majority of experience with umbilical cord blood (CB) centers on hematopoietic reconstitution, a recent surge in the knowledge of CB cell subpopulations as well as advances in ex vivo culture technology have expanded the potential of this rich resource. Because CB has the capacity to generate the entire hematopoietic system, we now have a new source for natural killer, dendritic and T cells for therapeutic use against malignancies. This Review will focus on cellular immunotherapies derived from CB. Expansion techniques, ongoing clinical trials and future directions for this new dimension of CB application are also discussed.