The 1.6 Å resolution structure of the Vibrio vulnificus arginine repressor was determined by molecular replacement using two models: (i) C-terminal domain of Escherichia coli arginine repressor/L-arginine complex (PDB code 1XXB); and (ii) the Reovirus outer capsid protein Sigma (3PDB code 1FN9). The first model was successful in finding a structure solution for a C-terminal domain of the protein, whereas the second structure was useful in finding solution for a N-terminal domain of the arginine repressor. The asymmetric unit is comprised of a single polypeptide chain with an alpha/beta fold. The N-terminal domain has three antiparallel helices and a two-stranded antiparallel β-sheet. The C-terminal domain contains a four-stranded antiparallel β-sheet and three antiparallel helices. Residues 71-76 that link the two domains are disordered in the structure. The C-terminal domain sits on a 3-fold crystallographic axis creating a trimer (buried surface area is 4380 Å2) with another two symmetry-related molecules. Another possible oligomer in the crystal is a hexamer (buried surface area is 14430 Å2) that is formed from two trimers positioned back-to-back along the aforementioned axis.