This study explores the morphological and structural transformation of boehmite (AlOOH) into transition aluminas during calcination, a pathway crucial for diverse industrial applications. The primary focus is on the topotactic transformation of boehmite into γ‐Al 2 O 3 and its subsequent transitions into higher temperature polymorphs, culminating in α‐Al 2 O 3 . Utilizing a combination of in situ X‐ray diffraction, in situ and ex situ transmission electron microscopy, 27 Al solid‐state nuclear magnetic resonance, thermogravimetric analysis, nitrogen physisorption, and mercury porosimetry, this work provides insights into the morphological and structural reordering during the calcination process. Furthermore, the study highlights the significant impact of thermal processing on the morphological evolution of boehmite and transition aluminas, characterized by changes in pore structure sizes and shapes. These findings offer valuable insights for optimizing the properties of alumina‐based materials for specific applications.