The HERMES instrument is a high resolution multi-object fiber-fed spectrograph (R~30,000) in development for the Anglo-Australian Telescope (AAT), covering the wavelength range (370-1000 nm). Given the sophistication of HERMES we have developed an end-to-end data simulator that accurately models the predicted detector images. The data simulator encompasses all aspects of the transmission and optical aberrations of the light path: from the science object, through the atmosphere, telescope, fibers, spectrograph and finally the camera detectors. The simulator uses optical information derived from ZEMAX software that has been processed and verified using MATLAB software. The simulator is sufficiently flexible to model other fiber spectrographs. In addition to helping validate the instrument design, the resulting simulated images will be used to develop the required data reduction software. In this paper, we present the simulator overview, requirements, specifications, system model, verification and simulation results.