[2] Indium(III) iodide is a pale yellow, very hygroscopic monoclinic solid (space group P21/c (space group no.

[5] In the presence of water vapor, the compound reacts with oxygen at 245 °C to form indium(III) oxide iodide.

The red form undergoes a transition to the yellow at 57 °C.

The structure of the red form has not been determined by X-ray crystallography; however, spectroscopic evidence indicates that indium may be six coordinate.

[7] The yellow form consists of In2I6 with 4 coordinate indium centres.