In this work, we report the fabrication of hierarchical nanofiber bundles from a perylene monoimide molecule that enable the sensitive detection of various inert volatile organic compounds (VOCs). We demonstrate that the internanofiber spacing of the bundles with appropriate packing interactions can be effectively adjusted by various VOCs, which is in turn translated into the dynamic fluorescence responses. Upon further decreasing the size of the nanofiber bundles, of which the internanofiber spacing is more favorably adjusted, enhanced fluorescence responses to various VOC vapors can be achieved. Our work presents a new protocol, i.e., translating the stimuli-responsive internanofiber spacing into fluorescence responses, to construct novel fluorescence sensors for various hazardous chemical vapors.