The pseudokinase complement of the human kinase superfamily consists of approximately 60 signaling proteins, which lacks one or more of the amino acids typically required to correctly align ATP and metal ions, and phosphorylate protein substrates. Recent studies in the pseudokinase field have begun to expose the biological relevance of pseudokinases, which are now thought to perform a diverse range of physiological roles and are connected to a multitude of human diseases, including cancer. In this review, we discuss how and why members of the `pseudokinome' represent important new targets for drug discovery, and describe how knowledge of protein structure and function provides informative clues to help guide the rational chemical design or repurposing of inhibitors to target pseudokinases.