Twinning-induced plasticity (TWIP) steel, having a great potential in applications in the automotive industry as a new generation of advanced steels, has attracted much attention in recent years because of the excellent combinations of strength and ductility resulting from deformation twinning. The monotonic tension behavior of TWIP steels has been extensively investigated; however, the serration behavior and low-cycle fatigue (LCF) properties have not been well understood. In order to obtain a good understanding of the mechanisms of room temperature serrated flows and the cyclic deformation behavior, the monotonic tensile deformation and fully reversed tension-compression LCF behaviors along with the deformed microstructures of an annealed TWIP steel were investigated in the present work. Both monotonic and fatigue tests were performed at room temperature with a strain rate of 6×10^-3 s^-1. The fatigue tests were conducted under total strain amplitude control with strain amplitudes ranging from 0.002 to 0.01. The tensile results show that the serrated plastic flows of stress-strain curves, presenting distinct characteristics at various strain levels, exhibit strong strain-level sensitivity. With increasing strain, the type A serrations featured by fine step-like flow are gradually replaced by the largely increased amplitude of type A serrations and their oscillation frequency decreases apparently; however, the frequency of type B serrations increases and the amplitude reduces slightly. The LCF fatigue results show that high cyclic hardening capacity is exhibited at all strain levels. At low strain amplitudes, the steel exhibits a very small initial cyclic hardening followed by a long saturation untill fracture. At medium strain amplitudes, a moderate initial cyclic hardening is followed by different degrees of cyclic softening depending on the applied strain amplitude, and then saturation untill fracture. At high strain amplitudes, the steel shows a rapid cyclic hardening quickly followed by softening till final fracture, almost without a saturation stage. Furthermore, at higher strain amplitudes, cyclic loading is found to lead to the generation of fine deformation twins in addition to high density of dislocation substructures, including dislocation walls and cell-like structures.