The phase precipitated in an Mg-Y-Nd alloy during ageing was studied using electron microscopy. Observations were performed along the orientations paralleling to [0001] and [11 (2) over bar0] zone axes of the matrix. The results showed that the platelike p phase has three variants growing along three <1120> directions of the matrix, the beta phase grew faster along <0001>(alpha) and <1120>(alpha) directions than along the third direction (<1 (1) over bar 00>). The morphology of the beta phases was illustrated according to the analysis of the directional misfit between the beta phase and the matrix.