The temperate Staphylococcus aureus phage ${Phi}11$ harbors cI and cro repressor genes similar to those of lambdoid phages. Using extremely pure ${Phi}11$ Cro (the product of the ${Phi}11$ cro gene) we demonstrated that this protein possesses a single domain structure, forms dimers in solution at micromolar concentrations and maintains a largely $alpha$-helical structure even at $45^{circ}C$. ${Phi}11$ Cro was sensitive to thermolysin at temperatures ranging from $55-75^{circ}C$ and began to aggregate at ${sim}63^{circ}C$, suggesting that the protein is moderately thermostable. Of the three homologous 15-bp operators (O1, O2, and O3) in the ${Phi}11$ cI-cro intergenic region, ${Phi}11$ Cro only binds efficiently to O3, which is located upstream of the cI gene. Our comparative analyses indicate that the DNA binding capacity, secondary structure and dimerization efficiency of thermostable ${Phi}11$ Cro are distinct from those of P22 Cro and $lambda$ Cro, the best characterized representatives of the two structurally different Cro families.