The increasing rate of cancer diagnosis and mortality has created an augmented need for new drugs and innovative strategies to battle cancer. During the pregenomics era, drug design was geared towards promoting cytotoxicity to the tumor cells, which due to lack of precision, killed a number of surrounding, healthy cells. Then came more rationally designed, target-based drugs that relied on the identification of signaling pathways that are deregulated in a specific type of cancer. Of these, immunotherapy was viewed as one of the best strategies to combat the disease, but it has proved difficult to achieve its maximum capability. Developing new drugs is cost prohibitive, but repurposing existing ones has proven to be promising and cost effective. In this review, we discuss some of the popular existing drugs that have immunomodulatory properties and therefore the potential for repurposing as immunotherapy against cancers.