<p>This study investigates the stress relaxation characteristics of bituminous mortars subjected to torsion. The bituminous mortar specimens are prepared using two distinct production processes. The first specimen is cored from a full bituminous mixture with a nominal maximum aggregate size of 13.2 mm, while the second specimen is designed to represent the mortar section of the bituminous mixture with the same nominal maximum aggregate size. Stress relaxation tests are conducted at various strain levels and temperatures. The linear viscoelastic limits of the mortar specimens are identified using scaling and superposition principles. The relaxation modulus in the linear regime is modelled using generalised Maxwell models, and the parameters are used to produce master curves. Relaxation spectra are also developed for the isothermal data. The findings reveal that specimens with smaller aggregates have a higher linearity limit and relax faster than those with larger aggregates. The generalised Maxwell model and relaxation spectra show that specimens with smaller aggregates have longer relaxation times.</p>