Effects of temperature and strain rate on tensile properties in a lean duplex stainless steel S32101 were investigated. The 0.2% proof stress and tensile strength increase with a decrease in the temperature and an increase in the strain rate. The uniform elongation decreased with an increase in the strain rate. In the temperature dependence on uniform elongation, it increased from 273 K to 283 K and indicated the maximum uniform elongation at 258 K. This is closely associated with TRIP effect because austenite is transformed to stress-induced martensite at temperatures below 283 K from the x-ray diffraction experiments. The stress-induced transformation behavior at 258 K, at which the maximum uniform elongation was obtained, had things in common with the case of metastable austenitic stainless steels. When the tensile properties were compared between the S32101 and the metastable austenitic stainless steels, the increase in the uniform elongation due to TRIP effect was almost the same. At low temperatures below about 250 K, the uniform elongations of the metastable austenitic steels were smaller than that of the S32101 because of the large amount of stress-induced martensite at small strains.