ZSM-5 aggregates were prepared using a quite small amount of colloidal silicalite-1 as active seed. The obtained ZSM-5 aggregates are well crystallized, possessing large external surface area, mesopore volume, and relatively regular mesopore size distributions. The as-prepared hierarchically porous ZSM-5 aggregates could be directly ion-exchanged to get the acidic H-form zeolite without calcination. When used as catalyst for the LDPE catalytic cracking, the obtained hierarchical ZSM-5 exhibited extinguished catalytic performances. This method for the preparation of hierarchically porous ZSM-5 is much more eco-friendly and cost-effective by avoiding the use of a large amount of organic structure-directing agent and the subsequent combustion of the occluded organic species. It can be easily scaled up and might be of great potential uses in the industrial processes.