Lath-shaped Mg2Sn precipitates with their habit planes parallel to the prismatic planes of the Mg matrix are characterized in a Mg-Sn-Zn-Mn alloy. The orientation relationships (ORs) between these beta-Mg2Sn precipitates and alpha-Mg matrix are [0 1 1](beta)//[0 1 -1 0](alpha) and (0 1 -1)(beta) deviating 0.36A degrees to 1.20A degrees from (0 0 0 1)(alpha), in which the deviation angle of 0.39A degrees is most frequently observed. Although the ORs vary, the laths always exhibit four side facets bearing fixed relationships with g vectors in reciprocal space. Their major side facets incline to the basal plane of Mg matrix from 4.3A degrees to 14.3A degrees.