Hierarchical structured ZSM-5 zeolite of c-axis-oriented nanorods has been prepared by a zeolite-seed-assisted hydrothermal synthesis method without any type of mesoscale template. The final product has loose aggregation which consists of rod-like nanocrystals with widths of about 20-30 nm, formed by the oriented aggregation model. The nitrogen physisorption suggested that the hierarchical structured ZSM-5 zeolite had higher mesopore volume and external surface area than the sample prepared conventionally. Due to the shortened microporous channel and opening mesopore, the prepared HZSM-5 catalyst presents high catalytic activity and stability for the alkylation of phenol with isopropanol. (C) 2010 Elsevier Inc. All rights reserved.