The past two decades have witnessed the booming of DNA aptamers, and particularly the development of aptamers for the specific recognition of versatile disease-related molecular biomarkers and living cells, as well as the application of aptamers for molecular and cellular engineering, bioanalysis, and disease therapy. Owing to the predictable Watson-Crick base-pairing, DNA can be easily designed and engineered to construct sophisticated molecular devices and nanostructures, which, at the same time, can be integrated with many biofunctionalities, including DNA aptamers for specific target recognition, bioimaging agents for biosensing, as well as drug-loading moieties for targeted drug delivery. The ability of many aptamers to mediate internalization into mammalian cells additionally empowered aptamer-incorporated DNA devices to be utilized for intracellular delivery of biosensors and drug carriers, and eventually sensing intracellular biomolecular behaviors in real-time or modulating intracellular biological activities for therapeutic purposes. In this chapter, we discuss the development of aptamerintegrated DNA nanodevices for versatile applications in bioanalysis and disease therapy, with an emphasis on cancer theranostics.