We have characterized the magnetic and structural properties of pure and 57Fe-doped La2/3Ca1/3MnO3 thin films and targets, substituted with 1% and 3% of 57Fe on the Mn site. The films were prepared via high O2-pressure (500 mTorr) by DC magnetron sputtering on (1 0 0) SrTiO3 and (1 0 0) LaAlO3 single-crystal substrates. Mössbauer spectra measured at room temperature confirm the presence of Fe3+ with octahedral coordination, thus indicating that Fe is incorporated into the structure by substituting Mn. Structural analysis by X-ray diffraction (XRD) shows that the films are single phase and c-axis oriented and that the Fe doping gives rise to a relaxation of the epitaxial strain. Interestingly, the Curie temperature and the magnetoresistance (MR) show a non-monotonic behavior with Fe doping. This indicates that initially the strain relaxation induced by the Fe doping is more important than the reduction of ferromagnetic coupling due to the Fe incorporation.