Recently, boron compounds have attracted increasing attention both in academic laboratories and in the pharmaceutical industry. Boron, in particular the 10B isotope, has the unique capability of absorbing a slow neutron to initiate a nuclear reaction with release of energetic particles such as α- and Li-particles, which is not observed in its carbon analogues. The nuclear capture reaction concept has been adopted in radiation therapy and used in boron neutron capture therapy (BNCT). BNCT is a potentially promising treatment for malignant brain tumors as well as other cancers, despite the limitation of a scarcity of neutron sources. There is the need in advanced research centers to construct high boron-containing composites as BNCT agents and develop more efficient drug carriers. This review discusses recent works on the development of boron-based therapeutic nanomaterials as BNCT agents.