Mechanical forces regulate development, homeostasis, and repair in the skin, lung, and cornea—external barrier organs that are exposed to stretch, shear, and stiffness. Dysregulated mechanotransduction drives fibrosis, inflammation, and impaired repair via conserved pathways [Piezo1 (Piezo-type mechanosensitive ion channel 1), TRPV4 (transient receptor potential vanilloid 4), and integrin–YAP (Yes-associated protein)]. Targeting these circuits with small molecules, biologics, or stiffness-tuned biomaterials offers a novel category of cross-organ therapies. As mechanosensitive pathways and mechanically informed biomaterials advance toward clinical testing, an integrated cross-organ perspective is urgently needed to address unmet therapeutic needs in chronic barrier diseases. This review unifies disparate insights into biophysics, molecular biology, and clinical practice to reveal how shared mechanisms underpin barrier pathologies and enable breakthrough mechanomedicine treatments.