Cancer vaccines have emerged as a powerful new tool for cancer immunotherapy. Adjuvants are vaccine ingredients that enhance the strength, velocity, and duration of the immune response. The success of adjuvants in achieving stable, safe, and immunogenic cancer vaccines has generated enthusiasm for adjuvant development. Specifically, advances in materials science are providing insights into the rational design of vaccine adjuvants for topical cancer immunotherapy. Here, we outline the current state of materials engineering strategies, including those based on molecular adjuvants, polymers/lipids, inorganic nanoparticles, and bio-derived materials, for adjuvant development. We also elaborate on how these engineering strategies and the physicochemical features of the materials involved influence the effects of adjuvants.