The intriguing properties of two-dimensional transition metal dichalcogenides (2D TMDCs) have led to a significant body of fundamental research and rapid uptake of these materials in many applications. Specifically, 2D TMDCs have shown great potential in biological systems due to their tunable electronic characteristics, unique optical properties, stability in aqueous environments, large surface area that can be manipulated and functionalized as well as an intercalatable layered structure, and low levels of toxicity. Here, the characteristics and use of 2D TMDCs for biological applications are reviewed and future possibilities for these materials in biological systems are outlined.