Self-assembly based on reversible metal-ligand bond formation is useful for the synthesis of discrete supramolecular nanoarchitectures. However, the architectures constructed by this technique sometimes suffer from kinetic instability due to the dissociation of metal-ligand bonds, especially under highly diluted conditions or in the presence of competitive ligands or metal ions. In this study, a kinetically stabilized metallomacrocycle was synthesized in one pot via the combination of metal-mediated self-assembly and subsequent oxidative "locking" of the coordination bonds. The macrocycle consists of four Co ions and four bis-bidentate ligands L(2-). The complexation of labile Co(II) ions with the ligands afforded the macrocycle with four-fold rotational symmetry, exhibiting the right-angled geometries of the β-diketonate ligands on the carbazole. The subsequent oxidation of the Co(II) ions inside the macrocycle into Co(III) ions made the metal-ligand bonds almost inert, thus affording a kinetically locked 4 : 4 metallomacrocycle. This macrocycle showed high stability even in the presence of an excess amount of competitive ligands. X-ray crystallography of the macrocycle indicated that it assembled in a columnar manner, forming one-dimensional nanochannels in the middle of the column.