The molar conductivity of RbBr solutions in 2-methylpropan-2-ol (tert-butanol) + water mixtures at alcohol mass fractions of 0.70, 0.80 and 0.90 was measured at temperatures from 288.15 to 308.15 K at 5 K intervals. The limiting molar conductivity (Δo) and the ion-pair formation constant (KoA) were determined by the Lee-Wheaton conductivity equation. Thermodynamic quantities, Gibbs energy (ΔGo), enthalpy (ΔHo) and entropy (ΔSo), for the ion-association reaction were derived from the temperature dependence of KoA; the activation energy of the ionic movement (ΔH*) was derived from the temperature dependence of Λo. These values were compared with those obtained earlier for HBr and NaBr in the same mixtures.