Abstract Temperature- and amplitude dependent internal friction (IF) of cold-worked, annealed and quenched Al–Mg alloys with 0.3–12 wt.%Mg is studied in the range from room temperature to 600 °C. Two thermally activated relaxation peaks, named P1 and P2 in the order of increasing temperature, are recorded. The first one (P1), with activation parameters H ≈ 1.1 eV, τ 0 ≈ 10 −13 s, relaxation strength Δ ≈ 0.008, and broadening parameter β τ ≈ 2 (for 1 Hz), is recorded only in Al–Mg alloys with 8–12%Mg predominantly in the as-quenched state, and classified as a Zener relaxation mechanism. The second one (P2, above 200 °C) is found at lower Mg contents (up to 5%) mainly in single-phase states (α solution of Mg in Al), with apparent parameters H ≈ 2 eV, τ 0 from 10 −16 to 10 −21 s, Δ up to 0.3 and β τ from 3 to 6. It is partly suppressed from the low-temperature side in Al–4Mg and Al–5Mg, due to precipitation of the β (Al 3 Mg 2 ) phase at the grain boundaries, and vanishes in the two-phase states of alloys with 8–12%Mg. The relaxation mechanism of P2 is associated with grain boundary sliding. At first heating from the cold-worked state, a recrystallization ‘pseudo’ peak is dominating in all alloys, whose position and height depend on degree of deformation, heating rate, vibrating frequency and chemical composition. Amplitude dependent damping measured during recrystallization demonstrates decreases in dislocation density and in critical stress for dislocation motion. Interaction energy ‘dislocation–point defects’ in Al–Mg alloys is estimated using amplitude dependent internal friction tests at different temperatures.