One aspect of the physiological ecology of intertidal organisms is their mechanical design, which can be explored at many hierarchical levels, from molecules to ecosystems. Mechanical structures, as with any other physiological feature, require energy to construct and maintain, are subject to manufacturing and evolutionary constraints, and influence ecological performance. This contribution focuses on the ecomechanics of mussel attachment, which contributes to the competitive dominance of mussels on many wave-swept shores. Examples are presented to illustrate the hierarchical nature of mussel attachment, how levels of the hierarchy are interrelated, and where gaps in our knowledge remain. For example, water motion generates forces that mechanically deform byssal threads, but may also enhance the rate at which threads subsequently restore their original toughness. Furthermore, the ability of mussels to sense and respond to changes in their flow environment by producing a stronger attachment may be subject to physiological constraints, which in turn may have important consequences for the ecological response of mussels to shifts in wave climate. Thus an integrative approach to the study of byssal attachment is needed to fully understand this important aspect of the physiological ecology of mussels on rocky intertidal shores.