We describe an example of “interpenetration isomerism” in three‐dimensional hydrogen‐bonded organic frameworks. By exploiting the crystallization conditions for a peripherally extended triptycene H6PET, we can modulate the interpenetration of the assembled frameworks, yielding a two‐fold interpenetrated structure PETHOF‐1 and a five‐fold interpenetrated structure PETHOF‐2 as interpenetration isomers. In PETHOF‐1, two individual nets are related by inversion symmetry and form an interwoven topology with a large guest‐accessible volume of about 80 %. In PETHOF‐2, five individual nets are related by translational symmetry and are stacked in an alternating fashion. The activated materials show permanent porosity with Brunauer‐Emmett‐Teller surface areas exceeding 1100 m2 g−1. Synthetic control over the framework interpenetration could serve as a new strategy to construct complex supramolecular architectures from simple organic building blocks.