<p>In a polycrystalline material, grain boundaries (GBs) play a critical role in tailoring the mechanical properties. While both coherent twin boundaries (CTBs) and incoherent twin boundaries (ITBs) influence the mechanical deformation mechanisms, literature tends to focus predominantly on the CTBs because of their ultrahigh stability and lack of atomic misfit. In contrast, the complex and disordered nature of ITB remains less explored. To bridge this gap, the authors have investigated the mechanical response of a nickel bicrystal containing faceted Σ3 [111] 60º {11 8 5} GBs under uniaxial compression loading. This special GB possesses both CTB and ITB facets arranged in an alternating manner. Molecular dynamics simulations were performed across a wide temperature (100 – 900 K) and strain rate (10⁷ – 10¹⁰ s⁻¹) range. The results revealed that the compressive yield stress decreased with increasing temperature and increased with increasing strain rate. Interestingly, the incipient plasticity phenomenon was observed ahead of the yield point for relatively lower strain rates. This incipient plasticity was found to be correlated with the dissociation of the ITB into distinct segments, followed by their subsequent coalescence. Furthermore, the incipient plasticity was marked by a sudden and small drop in the compressive stress-strain curve, corresponding to a sudden increase in the Shockley partial dislocation density. The emergence of intrinsic stacking faults (ISFs) at the tips of the ITB served as the compressive deformation mechanism for the failure of the configuration. These ISFs propagated throughout the material’s interior at lower strain rates; however, at higher strain rates, the ISFs exhibited an early distortion. Our findings provide a comprehensive atomic-level structural analysis of deformation behavior and an understanding of key mechanisms for incipient plasticity under compressive loading.</p>