The development of effective cancer vaccines depends heavily on the ability to deliver target antigens to generate an immune response. Dendritic cells are the most potent antigen-processing cells, capable of sensitizing T cells to new and recall antigens. Dendritic cells express high levels of major histocompatibility complex class I and II antigens, which are crucial to cancer immunotherapy, as well as a variety of important immunomodulatory proteins, adhesins, and a potent cytokine. Dendritic cells must undergo activation to induce an immune response, and this can be achieved through the use of certain carrier proteins, adjuvants, cytokines, or genetically engineered viruses. Dendritic cells are scattered throughout many tissues of the body, as well as bone marrow and peripheral blood. Most studies have used dendritic cells from peripheral blood; however, these cells are not prevalent in peripheral blood mononuclear cells. The cytokine, granulocyte-macrophage colony-stimulating factor, has been found to induce the maturation and enhance the viability of dendritic cells isolated from peripheral blood. Numerous clinical trials of antigen-pulsed dendritic cells have been conducted in various types of cancer, including non-Hodgkin lymphoma, multiple myeloma, prostate cancer, malignant melanoma, colorectal cancer, and non-small cell lung cancer. These studies show that antigen-loaded dendritic cell vaccinations are safe and promising in the treatment of cancer. This review discusses the use of dendritic cells in immunotherapy and some of the clinical trials that have been conducted.