[Fe] hydrogenase is a hydrogen activating enzyme that features a monoiron active site, which can be well characterized by Mossbauer spectroscopy. Mossbauer spectra have been measured of the CO and CN- inhibited species as well as under turnover conditions [Shima, S. et al., J. Am. Chem. Soc., 2005, 127, 10430]. This study presents calculated Mossbauer parameters for various active-site models of [Fe] hydrogenase to provide structural information about the species observed in experiment. Because theoretical Mossbauer spectroscopy requires the parametrization of observables from first-principles calculations (i.e., electric-field gradients and contact densities) to the experimental observables (i.e., quadrupole splittings and isomer shifts) nonrelativistic and relativistic density functional theory methods are parametrized against a reference set of Fe complexes specifically selected for the application to the Fe center in [Fe] hydrogenase. With this methodology, the measured parameters for the CO and CN- inhibited complexes can be reproduced. Evidence for the protonation states of the hydroxyl group in close proximity to the active site and for the thiolate ligand, which could participate in proton transfer, is obtained. The unknown resting state measured in the presence of the substrate and under pure H-2 atmosphere is identified to be a water-coordinated complex. Consistent with previous assignments based on infrared and X-ray absorption near-edge spectroscopy, all measured Mossbauer data can be reproduced with the active site's iron atom being in oxidation state +2.