This paper examined the fracture behavior of fiber bundles in moso bamboo by means of microscopic techniques. The fracture characteristics of fiber bundles in the tensile and compressive layer in response to three-point bending were analyzed. Results indicated that cracks propagate in a tortuous manner in three-point bending. The failure modes of fiber bundles were different in the tensile and compressive layer in bending. Specifically, two types of fiber fraction were observed in the tensile layer, namely smooth fracture and multistage delaminating. Three fracture modes were found in the compressive layer: minor cracks immediately under the area of loading head; localized fiber cracks in tension and delamination between fibers. Unique cellular arrangement, micro-cracks and crack deflection can increase elasticity, failure strength and flexibility of bamboo. The failure behavior of fiber bundles and tortuous crack propagation presented in this study can provide insights into the development of advanced bio-inspired materials and bamboo composites.