Significance Nanosheet HZSM-5 film vertically grown on the substrate with the tailorable macro- and meso-pores between the layers of nanosheets is hydrothermally synthesized by seed-assisted secondary growth method. The as-prepared nanosheet HZSM-5 film exhibits reaction rate enhancement up to 312% in catalytic cracking of n-dodecane as well as twice light olefins selectivity, ascribed to the better mass transfer of reactants in the hierarchical porous structure and the ultra-thin b-axis pores of nanosheets. (c) 2018 American Institute of Chemical Engineers AIChE J, 64: 1923-1927, 2018