DNA is polymorphic. Increasing evidence has indicated that many biologically important processes are related to DNA's conformational transition and assembly states. In particular, noncanonical DNA structures, such as the right-handed A-form, the left-handed Z-form, the triplex, the G-quadruplex, the i-motif, and so forth, have been specific targets for the diagnosis and therapy of human diseases. Meanwhile, they have been widely used in the construction of smart DNA nanomaterials and nanoarchitectures. As rising stars in materials science, the family of carbon nanomaterials (CNMs), including two-dimensional graphene, one-dimensional carbon nanotubes (CNTs), and zero-dimensional graphene or carbon quantum dots (GQDs or CQDs), interact with DNA and are able to regulate the conformational transitions of DNA. The interaction of DNA with CNMs not only opens new opportunities for specific molecular recognition, but it also expands the promising applications of CNMs from materials science to biotechnology and biomedicine. In this Account, we focus on our contributions to the field of interactions between CNMs and DNA in which we have explored their promising applications in nanodevices, sensing, materials synthesis, and biomedicine. For one-dimensional CNTs, two-dimensional graphene, and zero-dimensional GQDs and CQDs, the basic principles, binding modes, and applications of the interactions between CNMs and DNA are reviewed. We aim to give prominence to the important status of CNMs in the field of molecular recognition for DNA. First, we summarized our discovery of the interactions between single-walled carbon nanotubes (SWNTs) with duplex, triplex, and human telomeric i-motif DNA and their interesting applications. For example, SWNTs are the first chemical agents that can selectively stabilize human telomeric i-motif DNA and induce its formation under physiological conditions. On the basis of this principle, two types of nanodevices were designed. One was used for highly sensitive detection of ppm levels of SWNTs in cells, and the other monitored i-motif DNA formation. Further studies indicated that SWNTs could inhibit telomerase activity in living cells and cause telomere dysfunction, providing new insight into the biological effects of SWNTs. Then, some applications that are based on the interactions between graphene and DNA are also summarized. Combined with other nanomaterials, such as metal and upconversion nanoparticles, several hybrid nanomaterials were successfully constructed, and a series of DNA logic gates were successfully developed. Afterwards, the newcomer of the carbon nanomaterials family, carbon quantum dots (CQDs), were found to be capable of modulating right-handed B-form DNA to left-handed Z-form DNA. These were further used to design FRET logic gates that were based on the CQD-derived DNA conformational transition. Taking into account the remaining challenges and promising aspects, CNM-based DNA nanotechnology and its biomedical applications will attract more attention and produce new breakthroughs in the near future.