A photofunctionalized square bipyramidal DNA nanocapsule (NC) was designed and prepared for the creation of a nanomaterial carrier. Photocontrollable open/close system and toehold system were introduced into the NC for the inclusion and release of a gold nanoparticle (AuNP) by photoirradiation and strand displacement. The reversible open and closed states were examined by gel electrophoresis and atomic force microscopy (AFM), and the open behavior was directly observed by high‐speed AFM. The encapsulation of the DNA‐modified AuNP within the NC was carried out by hybridization of a specific DNA strand (capture strand), and the release of the AuNP was examined by addition of toehold‐containing complementary DNA strand (release strand). The release of the AuNP from the NC was achieved by the opening of the NC and subsequent strand displacement. An open and shut case: A square bipyramidal DNA nanocapsule (NC) was designed to create a nanomaterial carrier. A photocontrollable open/close system and toehold system were introduced into the NC for capture and release of a gold nanoparticle (AuNP) by photoirradiation and strand displacement. The encapsulation and release of the AuNP was successfully carried out by opening of the NC and strand displacement.