<p>The microstructural evolution and tensile properties of tempered martensite (TM) and annealed cold-rolled martensite (AM) steels with comparable hardness levels were examined to clarify the origins of their differing tensile behaviors. A low-carbon steel was quenched and then subjected either to tempering or to cold rolling followed by annealing, producing TM and AM steels with Vickers hardness values ranging from approximately 170 to 350 Hv. Microstructures were characterized using optical microscopy, tensile properties were evaluated through tensile testing, and dislocation substructures were quantitatively analyzed by x-ray line profile analysis. No recrystallization occurred in the TM steel even after long-term tempering, whereas recrystallization readily occurred in the AM steel during short-term annealing. Thus, the TM steel retained a lath-like ferrite grain morphology, while the AM steel developed fine, equiaxed recrystallized ferrite grains. Across all hardness levels, the TM steel exhibited higher tensile strength, whereas the AM steel showed greater total elongation. x-ray line profile analysis revealed that, at high hardness levels, the TM steel contained a high density of randomly distributed dislocations, while the AM steel exhibited a lower dislocation density accompanied by strong dislocation interactions. Differences in uniform and local elongation between the TM and AM steels varied with hardness level. These differences in tensile properties are attributed to variations in dislocation density and ferrite grain morphology arising from distinct recovery and recrystallization processes.</p>