To provide a radio tag installing member for a tire capable of stably housing a radio tag for fixation for a long time and capable of easily fitting the radio tag to a tire, while properly protecting the radio tag to be fitted to a tire from an impact and vibration, and to provide a pneumatic tire, to which the radio tag installing member for a tire is fitted, and an assembly of the pneumatic tire and a rim.

The radio tag installing member for a tire is provided with a sponge material 15 to be fixed to a rim installation side surface 10a of the pneumatic tire 10 or/and a pneumatic tire fitting side surface of the rim 11, and a radio tag provided with a tire inside condition detecting section or/and at least a tire discriminating information recording section. The radio tag is inserted into a housing part formed of a recessed part or a slit-like cut part, which is formed in the sponge material 15, for fixation, or the radio tag is fixed to a surface of the sponge material.