<p>Realizing invertible chiral optical properties in the visible region is crucial for developing optical systems with applications in displays and sensors. Achieving this with cellulose nanocrystal (CNC)-based materials is difficult because their chiral nematic structures are inherently fixed in a left-handed configuration. Here, we demonstrate that by introducing a unidirectional (or monodomain nematic-like) CNC hydrogel as a retardation layer onto a chiral nematic CNC film, the naturally left-handed chiral reflections of CNC films can be converted to right-handed reflections. Furthermore, the right-handed reflection can be switched back to their left-handed state simply by applying pressure. These mechano-responsive invertible chiral optical phenomena, along with the manipulation of light through the cooperation of unidirectional and chiral nematic CNC structures, opens up new opportunities for developing bio-based invertible chiral optics and sensors.</p>