jats:titleAbstract</jats:title> jats:pIn this work, we investigate the effect of anti-site disorder on the half-metallic properties of a Mnjats:sub2</jats:sub>FeAl Heusler alloy thin film. The film was grown on TiN-buffered MgO 001 substrates via magnetron sputtering. A detailed structural characterization using x-ray diffraction (XRD) and anomalous XRD showed that the film crystallizes in the partially disordered jats:italicL</jats:italic>2jats:sub1</jats:sub> jats:italicB</jats:italic> structure with 33% disorder between the Mn(B) and Al(D) sites. We measure a positive anisotropic magnetoresistance in the film, which is an indication of non-half metallic behaviour. Our x-ray magnetic circular dichroism sum rules analysis shows that Mn carries the magnetic moment in the film, with a positive Fe moment. Experimentally determined moments correspond most closely with those found by density functional calculated for the jats:italicL</jats:italic>2jats:sub1</jats:sub> jats:italicB</jats:italic> structure with Mn(B) and Al(D) site disorder, matching the experimental structural analysis. We thus attribute the deviation from half-metallic behaviour to the formation of the jats:italicL</jats:italic>2jats:sub1</jats:sub> jats:italicB</jats:italic> structure. To realize a half-metallic Mnjats:sub2</jats:sub>FeAl film it is important that the inverse Heusler jats:italicXA</jats:italic> structure is stabilized with minimal anti-site atomic disorder.</jats:p>