Lightweighting for bodies in white has become an important approach for enhancing energy efficiency and reducing emissions within the automotive industry. Among various lightweight materials, high-strength steel has shown considerable potential in terms of cost-effectiveness, safety, and user satisfaction. In particular, Fe-Mn-Al-C twinning-induced plasticity (TWIP) steel, also known as the third generation TWIP steel, has received considerable attention from the automotive industry in recent years owing to its excellent mechanical properties and good formability. During deformation, TWIP steel generates a considerable amount of deformation twinning within its grains, thereby impeding dislocation motion and resulting in high strain hardening rates in TWIP steels. Given that TWIP steels may be subjected to cyclic loading during actual service, the potential for fatigue failure poses a substantial risk during their long-term service, resulting in serious economic losses or human casualties. However, the deformation behavior and microstructure evolution of Fe-Mn-Al-C TWIP steel during low-cycle fatigue remain extensively understudied. Therefore, the study of the fatigue properties of TWIP steels is of considerable importance for their design and application in the automotive industry, warranting increasing attention. Herein, the low-cycle fatigue behaviors of Fe-22Mn-3Al-0.6C steels with different grain sizes were investigated. Steels with grain sizes of 8, 16, and 60 μm were prepared via hot rolling and subsequent heat treatment. After low-cycle fatigue testing, the samples were characterized using SEM equipped with electron channeling contrast imaging components and TEM. The effects of grain size on cyclic stress response, damage mechanisms, and fatigue life of Fe-Mn-Al-C TWIP steel were analyzed. Considering the fatigue damage contributed by strain and stress, the low-cycle fatigue property of TWIP steel was assessed from the perspective of hysteresis energy. Results indicated that the TWIP steel with small grain size (8 μm) exhibited enhanced low-cycle fatigue performance at a small total strain amplitude (Δε / 2 = 0.3%). Conversely, at a large total strain amplitude (Δε / 2 = 1.0%), the TWIP steel with large grain size (60 μm) exhibited enhanced low-cycle fatigue performance. Hysteretic energy model analysis revealed that fatigue damage mechanisms in TWIP steels were dominated by strain damage at large total strain amplitudes, with coarse grains showcasing an improved capacity to accommodate damaged defects. Conversely, at reduced total strain amplitudes, the fatigue mechanism was dominated by stress damage, with fine-grained steels showing enhanced strength and improved resistance against fatigue crack initiation.