Abstract Bamboo sliver (BS) is a potential elementary unit for multidimensional bamboo-based composites (MBBCs). Axial tensile and flexibility characteristics of thin radial (R) and tangential (T) BSs (BSR and BST with a thickness of 0.5–2.0 mm) have been studied. Axial tensile strength (AxTS) and modulus of elasticity (AxMOE) were positively correlated with the vascular tissue ratio (VTR), and the tensile properties of slices with 43–51% VTR increased more rapidly than in the VTR range of 20–36%. In axial tensile tests, cracks propagated along a V or Z route in BSR, while fibers were pulled out in the central section in case of BST. AxTS and AxMOE values increased with decreasing moisture content (MC) at 6.2–16.6% below 75°C. Flexural flexibility (FF) was enhanced with increasing MC and VTR, and the effect of MC on FF was amplified with MCs below the fiber saturation point (FSP). In situ scanning electron microscope (SEM) observation during flexural tests revealed a deformation resistance of vascular tissue (VT) and the deformation disposition of parenchyma.