A new strategy, zeolite seed-mediated alkaline steaming treatment, has developed for synthesizing hierarchically porous zeolite. This approach involves successive transformation from an initially amorphous mesophase to a crystallized mesophase with zeolite framework under alkaline steaming. This is the first demonstration that single-crystallized hierarchically porous MFI zeolite particles could be simply synthesized under alkali steaming assisted by a small amount of zeolite seeds. The mesoporosity and particle morphology of the obtained hierarchically porous zeolites can be well tuned by changing the composition of alkaline steaming. Steaming in alkaline vapor containing TBAOH and EDA, the synthesized hierarchically porous single crystalline MFI zeolite particles show an interlamellar sheet-packed oriented structure and highly developed mesoporosity with hierarchy factor (HF) of as high as 0.25 in comparison with most previous reports where HF values are lower than 0.20. This hierarchically porous zeolite shows capacious adsorption for heavy metal ions, such as Cu (II). (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.