In this study, we identify the crystal structures and elucidate the formation mechanism of Al–Mn(–Fe) intermetallic particles formed in Mg–Al-based alloys with varied Al contents, FeCl3 addition or melt superheating. The formed Al–Mn(–Fe) particles were collected through a newly developed particle extraction method for structural, chemical and morphological characterizations. It is found that increasing the Al content from 3 wt% to 9 wt% changes the major Al–Mn phase from τ-Al0.89Mn1.11 in AZ31 to γ2-Al8Mn5 in AZ91, and both FeCl3 addition and melt superheating promote the formation of γ2-Al8(Mn,Fe)5 in AZ31 and AZ63. In addition, through tuning FeCl3 addition level or melt superheating temperature, different morphologies of the γ2-Al8(Mn,Fe)5 particles are formed in AZ31 and AZ63, including quasi-cubes, octa-pod microstructures and polyhedral particles. This study provides several important approaches to control the crystal structure and morphology of Al–Mn(–Fe) intermetallic particles formed in Mg–Al-based alloys.