The compound adopts an edge-shared bioctahedral structure, which means that two NbI5 units are joined by a pair of iodide bridges.

[3] Niobium(V) iodide forms of dark, brassy, extremely moisture-sensitive needles or flakes.

The crystal structure consists of zigzag chains of corner-sharing NbI6 octahedra.

Since so far only twinned crystals of this phase have been obtained, and the structure determination is uncertain.

[4] If the reaction of the elements is carried out with an excess of iodine, a triclinic modification is created with the space group P1 (No.