Hierarchical FAU zeolites with house-of-card-like (HCL) structures were synthesized through a one-pot organotemplate-free route in the Na2O-Al2O3-SiO2-H2O system. The structure details and formation mechanism of HCL zeolites were determined by the combination of electron crystallography and synthesis chemistry. The results revealed that the unique HCL morphology was attributed to large solution viscosity, and the evolution process obeyed a skeleton crystal growth model due to the limited vortexing effect, which was different from those of the HCL zeolites obtained using organic templates.