Abstract In hot working of multiphase steels, the thermal history of the material before working affects the phase balance of the steel. The aim of this research is to investigate the influence of the thermal history before hot working on hot workability by performing hot uniaxial tensile tests. Duplex stainless steel was chosen as the experimental material because it has the typical dual-phase structure consisting of δ Ferrite and, Austenite and its phase balance changes with temperature. The phase ratio of δ Ferrite is higher at high temperatures, and the ratio of the relatively Austenite phase increases as the temperature decreases. In addition, part of the δ Ferrite phase transforms to the brittle Sigma phase at 1000°C and lower. The effect of the temperature history before working on hot workability was investigated with two thermal control patterns, cooling (Type I) or heating (Type II) from the holding temperature before hot working. To clarify the effect of the cooling and heating rates before hot working, two greatly different rates (0.1°C/sec, 10.0°C/sec) were used in both cooling (Type I) and heating (Type II). Under the Type I condition, the heating temperature was 1250°C, and the hot working test temperature was in the range of 650-1150°C. With the higher cooling rate, hot workability showed a large increase in the temperature range of 850-1150°C. This phenomenon was caused by retention of a high phase ratio of δ Ferrite at high temperature, together with inhibition of the transformation to the brittle Sigma phase at under 1000°C. Under the Type II condition with the heating temperature of 1050°C, hot workability was the same between different heating rates. On the other hand, when the holding temperature was 950°C, at which the Sigma phase forms, hot workability decreased drastically at hot working temperatures under 1100°C under the high heating rate condition. This phenomenon was caused by the remaining brittle Sigma phase and harder Austenite, which were not completely dissolved and transformed due to the high heating rate. Thus, with multi-phase steels in which the phase balance displays temperature dependence, it is important to select appropriate experimental conditions considering microstructural changes when evaluating hot workability with a combination of rapid cooling or rapid heating before the hot working.