Changes in the structure and mechanical properties of the billets from the cast nonage-hardenable complex-alloyed 1570C alloy (Al-5Mg-0.18Mn-0.2Sc-0.08Zr, weight%) were studied during multi-directional isothermal forging with decreasing temperature from 325 to 175°C up to cumulative strain e ≈ 24 and subsequent annealing in the temperature interval from 325 to 450°C. It is shown that the multi-directional forging with decreasing temperature can be an effective method providing processing of billets with ultrafine grain structure with the grain size up to 1-2 µm and a favorable combination of strength and ductility in the aluminum alloy 1570C.