CoI2 has two forms, α-from is a black crystal, density 5.58 g/cm³, melting point 515 ̊C; β-form is a yellow powder, density 5.45 g/cm³, and converts to α-form at 400 ̊C. It is hazardous and soluble in water.

CoI2 example reactions:
• 3SnI4 + 2Co3(PO4)2 = 6CoI2 + Sn3(PO4)4