It is a red solid with a metallic lustre that resembles copper in appearance.

[2] Rhenium trioxide crystallizes with a primitive cubic unit cell, with a lattice parameter of 3.742 Å (374.2 pm).

The structure of ReO3 is similar to that of perovskite (ABO3), without the large A cation at the centre of the unit cell.

At 300 K, its resistivity is 100.0 nΩ·m, whereas at 100 K, this decreases to 6.0 nΩ·m, 17 times less than at 300 K.[3] Rhenium trioxide is insoluble in water, as well as dilute acids and bases.

Heating it in base results in disproportionation to give ReO2 and ReO−4, while reaction with acid at high temperature affords Re2O7.